Summarize:

In an open letter to the Daily Telegraph, six ex-defence chiefs said interim measures to fill the gap left by the spy planes "fall far short".
They said the decision to destroy the aircraft, commissioned in 1993 and due to enter service in 2012, as perverse.
The government says taking Nimrod out of service will save £2bn in 10 years.
General Sir David Richards, Chief of the Defence Staff, said the move to cancel the Nimrod MRA4 had not been taken lightly.
Work on scrapping the nine planes began in Greater Manchester on Wednesday.
The letter's author, Air Vice Marshal Tony Mason, former air secretary to the RAF, said short-term cost cutting had been put ahead of long-term strategic needs.
He told the BBC: "My concern was not just that this exceptionally important programme had been cancelled for good but the total absence of reference to this strategic gap in our defences."
The Nimrod issue was later discussed in the House of Commons.
Shadow leader of the Commons, Hilary Benn, said: "Following the release of the extraordinary photographs showing the dismantling of the £4bn fleet... which will then apparently be sliced up in an industrial shredder, can we have a statement from the defence secretary on the letter that has been sent by six former defence chiefs today?"
SNP MP Angus Robertson said: "The wasteful destruction of the Nimrod fleet does leave a hole in national security and the communities where they should be based at RAF Kinloss."
But the Leader of the Commons, Sir George Young, blamed a "£38bn deficit in the defence budget which we inherited from the outgoing government."
He said: "The project was nine years late, it saw a cost increase of 300%, none of the nine aircraft were operational, only one was fully constructed and it had not passed its flight tests.
"Cancelling has saved £2bn over 10 years and since Nimrod MR2 was taken out of service last year the impact has been mitigated by using other military assets including type-23 frigates, Merlin anti-submarine helicopters and Hercules C-130 aircraft and working with allies and partners where appropriate."
The letter to the Telegraph was signed by Marshal of the RAF Lord Craig, the former chief of the defence staff and chief of air staff; Major General Julian Thompson, the commander of land forces in the Falklands conflict; Major General Patrick Cordingley, the commander of the Desert Rats in the Gulf War; and Admiral Sir John "Sandy" Woodward, commander of the naval task force in the Falklands.
They warn that national security will be dangerously exposed without the aircraft, which would have continued to provide long-range reconnaissance and surveillance, and protect the Royal Navy's Trident submarines.
The Ministry of Defence has also been accused of failing to advise ministers of the full cost and impact of the loss of the planes.
Almost £4bn has been spent on the project and it will cost £200m to scrap the aircraft and pay compensation to the manufacturers, BAE Systems.
A Ministry of Defence spokesman said: "Ministers and service chiefs have made clear that the decision in October's [defence review] not to bring the Nimrod MRA4 into service was difficult, but it will not be reversed and the dismantling process is under way.
"The severe financial pressures and the urgent need to bring the defence programme into balance meant we could not retain all existing programmes."
Some defence sources say there were safety fears over the new Nimrods, after difficulties during manufacture, though BAE Systems insists those were easily fixed, the BBC's defence correspondent Caroline Wyatt said.

Summary:

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Leading military figures have warned that scrapping the £4bn fleet of new RAF Nimrods will create a "massive gap" in British security.