BRITAIN is to enter a timeshare deal with France over its Rosyth-built £2.5billion supercarrier.
The agreement opens a new chapter in cross-Channel co-operation and ends centuries of British naval dominance.
David Cameron and French President Nicolas Sarkozy will sign two treaties at an Anglo-French summit in London today that will also see the countries share nuclear missile research facilities and set up a joint fighting brigade.
The timeshare carrier deal will make the HMS Prince of Wales - due to be in service in 2020 - available to the French while their Charles De Gaulle carrier is being refitted.
The French carrier will be available for the British government when the Royal Navy supercarrier is undergoing refits.
But each country will have a veto on where their ship is sent.
This means that the French could prevent the British sending a fleet to the Falklands with a French carrier, for example, if it did not agree with the mission objectives.
The deal is vital because the first British supercarrier, HMS Queen Elizabeth - currently being assembled in Rosyth - is to be mothballed under defence cuts.
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The HMS Prince of Wales, the second carrier, is to be converted to enable French and US aircraft to fly off its decks.
There will be no aircraft for the carriers until 2020 as Harrier jet squadrons are being disbanded in cuts. But British and French forces will come together in a "combined joint expeditionary force" from next year.
The force will have just one commander and be under joint political control.
Nuclear co-operation will see both countries share research facilities.
Defence officials said the plan will not lead to a shared nuclear deterrent. While test facilities will be shared, warheads will be tested by each country's own staff.
Senior military sources said there are no plans "at this stage" to share the maintenance of the Royal Navy supercarrier HMS Prince of Wales with France.
Last night, Gordon Brown returned to the political fray with a call for servicing work to stay at Rosyth - saving 1500 jobs.
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In his first Commons speech since losing the general election, the former PM asked defence minister Peter Luff if the carriers would be serviced in Britain.
Luff replied: "I think it is extremely likely that they will - I cannot give a categorical assurance at this stage."