SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 6-K

REPORT OF FOREIGN ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16 OF
THE SECURITIES EXCHANGE ACT OF 1934

Date: 17 November 2005

NATIONAL GRID plc

(Registrant’s Name)

1-3 Strand
London
WC2N 5EH

(Registrant’s Address)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3- 2(b) under the Securities Exchange Act of 1934.

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b):

National Grid plc

Results for the six months ended 30 September 2005

Strong earnings growth. Positive outlook.

•     Earnings per share up 12%

•     Strong operating performance

•     Successful completion of gas network sales

•                  £2.5bn profit on disposal

•                  £2bn return of value to shareholders

•     Capital investment on track to increase from £1.5bn to £2bn per annum

Financial highlights - £ million (except where indicated)

* Not meaningful.

Sir John Parker, Chairman, said:

“National Grid continues to deliver strong operating performance, strong earnings growth and strong cash flows. This has been accompanied by our constant focus on safety and security of delivery. In addition, we are significantly increasing our level of investment over the medium term, which will support the Group’s future profit and dividend growth.

“In August, the Group returned £2bn to shareholders, one of the largest returns of value seen in the UK, following the successful completion of our UK gas distribution network sales.

“The Board has approved an interim dividend of 10.2p per ordinary share and views National Grid’s prospects with confidence and, accordingly, in line with our stated dividend policy, targets a 7% increase in the full 2005/06 dividend.  With this increase, the dividend per share will have grown by almost 60% since the merger with Lattice.”

Note A: Business performance results are the primary financial performance measure used by the Group, being the results for continuing operations before exceptional items and certain non-cash mark-to-market remeasurements of commodity contracts and financial instruments that are held for economic hedging purposes but which did not achieve hedge accounting.  Further details are provided in ‘Statutory Results and Business Performance’ on page 7.

Note B: “Constant currency basis” refers to the reporting of the actual first half results against the prior year first half results which, in respect of any US$ currency denominated activity, have been retranslated using the average US$ exchange rate for the six months ended 30 September 2005, which was $1.85 to £1.00. The average rate for the six months ended 30 September 2004 was $1.80 to £1.00.

National Grid
2005/06 Half Year Results

FINANCIAL RESULTS PRESENTATION

National Grid is reporting its results for the first time under IFRS.  The comparative results for the six months ended 30 September 2004 and for the fiscal year ended 31 March 2005 have also been presented on an IFRS basis and therefore differ from the UK GAAP results that have previously been published.

Unless otherwise stated, all financial commentaries are given on a business performance basis. Business performance represents the results for continuing operations before exceptional items and certain non-cash mark-to-market remeasurements of commodity contracts and financial instruments which do not relate to the Group’s underlying business performance.  Commentary provided in respect of results after exceptional items and certain non-cash mark-to-market remeasurements are described as ‘statutory’.

OVERVIEW

National Grid continues to deliver strong operating performance, producing growth in operating profit of 7% at constant currency, a 32% growth in continuing operating cash flows to £1.3bn and a 12% increase in basic earnings per share. This underpins the Group’s strongly progressive dividend policy of 7% increases each year through to March 2008.

The half-year results have been driven by continued residential volume growth in the US, a continued focus on efficiencies, particularly in UK gas distribution, favourable results from UK capacity auctions in liquefied natural gas (LNG) storage and the French interconnector, and a full-period contribution, in line with expectations, from Crown Castle UK(1).  The strong performance, aided by weather effects, more than offset an under recovery of commodity costs in the US (which will be recovered in full in future periods), a higher effective tax rate following the impact of changes to the UK tax environment, a weaker US dollar and the absence in the current period of certain one-off benefits recognised in the prior period.

In June, the Group successfully completed the sales of four of its UK gas distribution networks (network sales), receiving cash proceeds of £5.8bn, and in August returned £2bn of value to shareholders. The retained UK gas distribution business remains the largest in the UK, and its configuration is enabling the rapid and effective implementation of the ‘Way Ahead’ programme.

National Grid’s future profit growth is expected to be driven by achieving further efficiency gains, volume growth in the US and the returns on planned investment in its current businesses. The Group’s total annual investment is projected to grow by one-third, from £1.5bn to £2bn this year and remain at that level over the medium term. In particular, this reflects changing energy infrastructure requirements as the UK’s dependency on gas imports and its focus on renewable energy sources both increase along with the need to increase the rate of asset replacement in UK electricity transmission.  As planned, UK gas distribution replacement expenditure, half of which is added to the regulatory asset base, has increased 10% over the same period last year.

Investment for future growth is also expected in other Group operations.  The switchover to digital television is projected to require around £350m to £450m of industry investment between 2008 and 2012.  The Group believes National Grid Wireless is well placed to secure a significant portion of this investment.  By 2008, the Group will have invested £500m in the Isle of Grain LNG importation terminal.  Market appetite for further expansion at the Isle of Grain is currently being explored.

(1) National Grid acquired the UK assets of Crown Castle International Corp. on 31 August 2004.  For the six months ended 30 September 2004 there was a one month contribution from this business.

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REVIEW OF GROUP RESULTS

National Grid’s operating profit increased by 7% to £1,091m, up £74m from £1,017m, on a constant currency basis.  This was driven by continued volume growth in the US, a sustained focus on efficiencies throughout the Group, particularly in UK gas distribution, favourable results from UK capacity auctions in LNG storage and the French interconnector and a full-period contribution from Crown Castle UK that was in line with expectations.  Beneficial weather effects, primarily in the US, also increased operating profit.  These factors more than offset a significant under recovery of commodity costs in the US and the absence in the current period of certain one-off benefits recognised in the same period last year.

Net finance costs decreased 5% from £334m to £317m. This was primarily the result of a decrease in average net borrowings following the network sales, which completed on 1 June 2005, partially offset by higher interest rates.

Profit before tax was up 11% to £776m from £697m.

The tax charge on profit for the period was £246m, £42m higher than the prior period due to increased profit before tax and a higher effective tax rate of 32%.  This rate reflected the change in the mix of Group profit following the network sales and the impact of changes to the UK tax environment.

The weaker US dollar reduced operating profit by £13m, but the net exchange rate impact on earnings, after interest, tax and minority interests, was £7m.

Earnings increased 7% from the same period last year to £528m from £493m, while earnings per share, which benefited from the share consolidation which took place on 1 August, increased 12% from 16.0p last year to 17.9p.  The Group’s seasonally more significant second half, due to increased winter gas usage in the UK, will reflect in full the share consolidation with a consequential impact on EPS.

Exceptional items and remeasurements comprised restructuring costs of £25m (£18m net of tax), exceptional finance charges of £35m (£27m net of tax), commodity remeasurements of £22m (£13m net of tax) and financial instrument remeasurement gains of £42m (£29m gain net of tax).  After these items, and minority interests of £2m, statutory earnings for the period for continuing operations were £499m.

Statutory basic earnings per share from continuing operations increased 17% to 16.9p, up from 14.5p last year.

The Group’s cash flows grew very strongly with operating cash flow from continuing operations up 32% to £1.3bn from £1.0bn.

National Grid’s investment in continuing operations increased significantly (15%) to £827m from £722m compared with the same period last year.  Investment in UK electricity transmission increased by £51m, primarily due to overhead line replacement.  Work has commenced on the Milford Haven gas transmission project where the Group expects to invest around £450m through to 2008.  As planned, UK gas distribution replacement expenditure, capitalised under IFRS, also increased, up from £126m to £139m.  Investment in the Group’s Other businesses decreased in this period as the Basslink project undertaken by National Grid Australia nears completion; however, investment is expected to increase by year end as the Isle of Grain Phase II spend increases in the second half.  The full-year level of investment for the Group is projected to be around £2bn.

Group net debt was £11.1bn as compared with £14.0bn at 1 April 2005. This reflected the receipt of £5.8bn upon completion of the network sales in June 2005, the £2bn return of value to shareholders in August 2005, the increase in capital investment and normal seasonal factors.  Net debt, excluding the remeasurement effects of IAS 39, is expected to remain around this level for the remainder of the year as the increased capital investment programme is expected to offset normal seasonal cash inflow.

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An interim dividend of 10.2p per ordinary share ($0.8816 per American Depositary Share (ADS)) will be paid on 25 January 2006 to shareholders on the register as at 2 December 2005.

REVIEW OF OPERATIONS

A segmental analysis of the Group’s business performance is presented below:

*Not meaningful.

TRANSMISSION

*Other includes LNG storage and the French interconnector.  The Scottish interconnector is included in ‘UK electricity transmission’ in both periods.

** Not meaningful.

Operating profit from UK electricity and gas transmission was up 2% at £397m compared with £388m last year. This increase reflected higher gas Transmission Owner income, up £16m primarily from capacity auctions, as well as higher capacity auction income earned from both the Group’s LNG storage business and its French interconnector which are up a combined £26m from last year. This reflected the high demand from market participants for both LNG storage and interconnector capacity.  The higher auction income was partially offset by an increased Transmission Owner depreciation charge of £11m, a non-recurring one-off benefit to the same period last year of £15m, and lower revenues under the connections charging reform (‘Plugs’), the benefit of which decreased by £8m.

The Group is currently working with Ofgem on the extension of the UK electricity transmission price control by one year to April 2007.  In September, Ofgem published its initial proposals for the mini review to which the Group responded in October.  Final proposals from Ofgem are expected later this month.  Over the next twelve months, the Group will continue to work with Ofgem on the five-year electricity and gas transmission price control review.

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In the US, operating profit from US electricity transmission was stable at constant currency.

In August, the US Congress passed the Energy Policy Act of 2005.  While the new law is not expected to have any immediate effect on the Group’s business, certain provisions, including transmission pricing incentives and the creation of National Interest Transmission Corridors, may benefit National Grid’s long-term US strategy.

UK GAS DISTRIBUTION

Operating profit from the continuing UK gas distribution business was up 21% at £94m compared with £78m last year.  This reflected a very strong performance on costs, with operating expenditure (excluding shrinkage) reduced by £19m through realisation of the benefits of the Way Ahead programme.  Business rates were £11m higher than last year but are now being recovered as part of an average price increase of 4.6% implemented on 1 October 2005.  Shrinkage gas costs, which in this period increased by £2m, are forecast to increase further during the winter due to higher commodity costs.

The business remains on track to meet its cost reduction target by March 2007.  Controllable costs for the four retained networks, excluding increases in ongoing pension costs and shrinkage gas commodity prices, have decreased by 4% in real terms since March 2005 and have now decreased 24% in real terms since March 2002.  This is equivalent to cumulative savings in excess of £110m.

US DISTRIBUTION

The strength of US electricity and gas distribution’s performance was partially masked by an under recovery of commodity costs. Operating profit for US electricity and gas distribution was up 2% at £170m on a constant currency basis compared with £166m last year.  This good performance, which more than offset the under recoveries of £25m for the first six months of the year (compared to an under recovery of £5m last year), was primarily driven by volume growth and a continued focus on cost efficiencies.

(2) Stranded cost recoveries relate to costs incurred by the former generation businesses that National Grid sold during industry restructuring in the US.  These costs are recovered in accordance with the Group’s US rate plans.

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Under National Grid’s existing rate plans in the US, commodity costs are recovered in full from customers, although the profile of recovery may differ from the pattern of costs incurred.  Substantial rate increases were approved in September in both Massachusetts and Rhode Island to recover the higher commodity cost of electricity.  These rate increases have already been implemented.  In New York, commodity cost adjustments are made each month.

The operating profit contribution from US stranded cost recoveries for this period was £251m. This comprises the ongoing recovery of and return on the stranded cost base amounting to £173m, as well as £57m primarily related to the recovery of payments made under certain long term purchased power arrangements.  This segment has also benefited from a settlement reached with USGen New England, Inc. following the resolution of that company’s bankruptcy filing which resulted in £21m of operating profit.

Across the US Distribution business, electricity delivery volumes increased 4.8% compared to the prior year.  Excluding the effects of weather, higher margin residential sales deliveries increased by 2%, contributing to a £10m increase in operating profit.  The period-on-period weather effect increased operating profit by some £21m, primarily due to a warmer summer than last year.

US controllable costs were reduced by 2% in real terms since March 2005 as the business has continued its focus on cost efficiencies.

WIRELESS INFRASTRUCTURE

*Not meaningful

Operating profit for Wireless infrastructure was £36m, up from £8m and reflected a full period contribution from the enlarged business.   These results are in line with expectations.  Strong performance in broadcast and the realisation of integration savings more than offset a softening in demand for mobile infrastructure.  Continuing advances in digital compression technology have enabled the business to create additional channel capacity.  Two channels have been sold to ITV and Channel 4 respectively and an auction for a third channel is currently underway.

National Grid Wireless has agreed to the continuation, on broadly similar terms, of its largest broadcast contract to deliver analogue television and radio services to the BBC.  This will run through to switchover in 2012 for television and 2013 for AM and FM radio.

OTHER BUSINESSES

Operating profit from the Group’s Other businesses, was up 9% at £75m compared with £69m last year.  Strong performance by National Grid Metering, primarily from cost efficiency gains made in the period, was largely offset by the expected lower profits from National Grid Property.  By their nature, property sales can vary from period to period depending on the number and mix of properties sold.  The Group nevertheless expects full year results for National Grid Property to be in line with its expectations as its portfolio of properties remains robust.

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Phase I at the Isle of Grain was commissioned in July and work on Phase II is well underway.  The return on investment is expected to be comfortably ahead of the Group’s weighted average cost of capital.  Cumulative investment has now reached £160m out of an expected £500m total spend, all of which is underpinned by 20-year contracts signed with BP, Centrica, Gaz de France and Sonatrach. The Group is currently assessing further development at the Isle of Grain.

The Group’s Basslink project in Australia, an interconnector project linking Victoria and Tasmania, supported by a long-term contract with Hydro Tasmania, is expected to commission in the second quarter of 2006.

STATUTORY EARNINGS AND BUSINESS PERFORMANCE

A reconciliation of business performance earnings to statutory earnings is presented below:

*Not meaningful

Exceptional items in the period comprised exceptional restructuring costs of £25m (£18m net of tax) and exceptional finance costs on the early redemption of debt and on the B share scheme of £35m (£27m net of tax).

Remeasurements comprised £22m (£13m net of tax) of negative non-cash mark-to-market movements in the carrying value of certain legacy commodity contract obligations, primarily index-linked swap contracts in the US, and £42m (£29m net of tax) of positive non-cash mark-to-market movements in the carrying value of financial instruments, primarily derivatives, that are held for economic hedging purposes, but which did not achieve hedge accounting.

The results of discontinued operations include two months of contribution from the four regional gas distribution networks that were sold on 1 June 2005.  A gain on disposal of £2.5bn was recorded in the first half in respect of these sales.

Further details of ‘discontinued operations’ and ‘exceptional items and remeasurements’ are given in Note 3 and Note 4 respectively in the ‘Notes to the Interim Announcement’ section.

OUTLOOK AND DIVIDEND POLICY

The Board continues to have high confidence in the Group’s ability to generate future profit growth, given its opportunities for capital investment and continuing cost efficiencies. The Group will continue to maintain its disciplined approach to both organic and strategic investment.

The Board has approved an interim dividend of 10.2p per ordinary share ($0.8816 per American Depositary Share (ADS)).  The interim dividend will be paid on 25 January 2006 to shareholders on the register as at 2 December 2005.  National Grid expects the total dividend for 2005/06 to be 7% higher than last year and, looking ahead, continues to aim to increase dividends per ordinary share expressed in sterling by 7% in each financial year through to 31 March 2008.  A 7% increase to the 2005/06 total dividend would deliver growth of almost 60% since the merger with Lattice.

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CONTACT DETAILS

National Grid:

An analyst presentation will be held at Deutsche Bank AG, 75 London Wall, London EC2N 2DB at 9:00 am (UK time) today.

Live telephone coverage of the analyst presentation - password National Grid

Telephone replay of the analyst presentation (available until 1 December 2005)

A live web cast of the presentation will also be available at www.nationalgrid.com

Photographs are available on www.newscast.co.uk

Cautionary statement

This announcement contains certain statements that are neither reported financial results nor other historical information. These statements are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Because these forward-looking statements are subject to assumptions, risks and uncertainties, actual future results may differ materially from those expressed in or implied by such statements. Many of these assumptions, risks and uncertainties relate to factors that are beyond National Grid’s ability to control or estimate precisely, such as delays in obtaining, or adverse conditions contained in, regulatory approvals, competition and industry restructuring, changes in economic conditions, currency fluctuations, changes in interest and tax rates, changes in energy market prices, changes in historical weather patterns, changes in laws, regulations or regulatory policies, developments in legal or public policy doctrines, the impact of changes to accounting standards, technological developments, the failure to retain key management, the availability of new acquisition opportunities or the timing and success of future acquisition opportunities. Other factors that could cause actual results to differ materially from those described in this announcement include the ability to continue to integrate the US and UK businesses acquired by or merged with National Grid, the failure for any reason to achieve reductions in costs or to achieve operational efficiencies, unseasonable weather impacting on demand for electricity and gas, the behaviour of UK electricity market participants on system balancing, the timing of amendments in prices to shippers in the UK gas market, the performance of National Grid’s pension schemes and the regulatory treatment of pension costs, the impact of the separation and sale by National Grid of four of its UK gas distribution networks and any adverse consequences arising from outages on or otherwise affecting energy networks owned and/or operated by National Grid.

For a more detailed description of these assumptions, risks and uncertainties, together with any other risk factors, please see National Grid’s filings with the US Securities and Exchange Commission (and in particular the “Risk Factors” and “Operating and Financial Review” sections in its most recent annual report on Form 20-F). Recipients are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this announcement. National Grid does not undertake any obligation to release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this announcement.

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(i)        Refer to note 1 for the basis of preparation of the comparatives presented under International Financial Reporting Standards.

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(i)        Refer to note 1 for the basis of preparation of the comparatives presented under International Financial Reporting Standards.

Net debt at 30 September 2004 and 31 March 2005 has not been adjusted to reflect the impact of IAS 39, which has been adopted from 1 April 2005 onwards.

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(i)        Refer to note 1 for the basis of preparation of the comparatives presented under International Financial Reporting Standards.

(ii)     The Group has adopted IAS 32 “Financial Instruments: Disclosure and Presentation” and IAS 39 “Financial Instruments: Recognition and Measurement” prospectively with effect from 1 April 2005, in accordance with the transition provisions of IFRS 1. As a result, the balance sheet at 31 March 2005 and 30 September 2004 and the income statement for the periods ended 31 March 2005 and 30 September 2004 exclude the effect of IAS 32 and IAS 39.

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