Britain and France will share crucial data needed to maintain nuclear stockpiles in a single shared facility.

Both the countries will build a shared test facility that will simulate nuclear explosions and determine whether nuclear warheads will be reliable as they age.

"I'm frankly effing baffled by this," says Jeffrey Lewis, an arms-control expert with the James Martin Center for Nonproliferation Studies in Washington DC. But Bruno Tertrais at the Foundation for Strategic Research in Paris says that the motivation is "extremely simple: to save money".

Both nations have so far built their nuclear weapons program independently.

The lab, which would cost $ 350 million to be build, will save both nations considerable sum of money.

The collaboration will include exchanges of nuclear researchers between the two labs, and, according to a press release from the office of French President Nicolas Sarkozy, create "a climate of trust" between scientists in the two countries.

"However, EPURE is designed to allow both countries to keep, for each experiment, full sovereignty over the results," the statement adds.