Report: "We have now obtained previously top-secret papers which show not only that Norway was a mere cover for the Israel deal, but that Britain made hundreds of other secret shipments of nuclear materials to Israel in the 1950s and 1960s."
Mirage jets swoop from the sky to destroy the Egyptian air force before breakfast; tanks race across the desert to the Suez Canal; Moshe Dayan, the defense minister, poses with eye patch after the Jerusalem brigade has fought its way into the Old City. These are the heroic images of the Six Day War and they defined Israeli daring: here was a people who, it seemed, risked everything on a throw of the dice. Years later the world discovered that there was an insurance policy.

They had a secret weapon – two, to be precise. In the weeks before Israel took on the Arab world in June 1967 it put together a pair of crude nuclear bombs, just in case things didn’t go as planned. Making them required not only Israeli ingenuity but also plenty of help from abroad. It has been known for some time that the French helped build Israel’s reactor and reprocessing plant at Dimona, but over the past year our research team at BBC Newsnight has unearthed something no less astonishing and much closer to home – top-secret files which show how Britain helped Israel get the atomic bomb.

We can reveal that while Harold Wilson was prime minister, the United Kingdom supplied Israel with small quantities of plutonium despite a warning from British intelligence that it might "make a material contribution to an Israeli weapons program". This, by enabling Israel to study the properties of plutonium before its own supplies came on line, could have taken months off the time it needed to make a weapon. Britain also sold Israel a whole range of other exotic chemicals, including uranium-235, beryllium and lithium-6, which are used in atom bombs and even hydrogen bombs. And in Harold Macmillan’s time we supplied the heavy water that allowed Israel to start up its own plutonium production facility at Dimona – heavy water that British intelligence estimated would enable Israel to make "six nuclear weapons a year".

After we exposed the sale of the heavy water on Newsnight last August, the government assured the International Atomic Energy Agency (IAEA) that all Britain did was sell some heavy water back to Norway. Using the Freedom of Information Act, we have now obtained previously top-secret papers which show not only that Norway was a mere cover for the Israel deal, but that Britain made hundreds of other secret shipments of nuclear materials to Israel in the 1950s and 1960s.

Tony Benn became technology minister in 1966, while the plutonium deal was going through. Though the nuclear industry was part of his brief, nobody told him we were exporting atomic energy materials to Israel. "I’m not only surprised," he says, "I’m shocked." Neither he nor his predecessor Frank Cousins agreed to the sales, he insists, and though he always suspected civil servants of doing deals behind his back, "it never occurred to me they would authorize something so totally against the policy of the government".

The documentary evidence is backed by eyewitness testimony. Back in August 1960, when covert photographs of a mysterious site at Dimona in Israel arrived at Defense Intelligence Staff (DIS) in Whitehall, a brilliant analyst called Peter Kelly saw immediately that they showed a secret nuclear reactor. Today Kelly, physically frail but mentally acute, lives in retirement on the south coast, and as he leafs through the "UK Eyes Only" reports he wrote about Israel for MI5 and MI6, he smiles. "I was quite perceptive," he says. Kelly recognized that the Dimona reactor was a French design, and he very soon discovered where the heavy water needed to operate it had come from. When we explain that the government has told the IAEA that Britain thought it was selling the heavy water to Norway he laughs heartily.

What really happened was this: Britain had bought the heavy water from Norsk Hydro in Norway for its nuclear weapons program, but found it was surplus to requirements and decided to sell. An arrangement was indeed made with a Norwegian company, Noratom, but crucially the papers show that Noratom was not the true buyer: the firm agreed to broker a deal with Israel in return for a 2 per cent commission. Israel paid the top price – £1m – to avoid having to give guarantees that the material would not be used to make nuclear weapons, but the papers leave no doubt that Britain knew all along that Israel wanted the heavy water "to produce plutonium". Kelly discovered that a charade was played out, with British and Israeli delegations sitting in adjacent rooms while Noratom ferried contracts between them to maintain the fiction that Britain had not done the deal with Israel.

The transaction was signed off for the Foreign Office by Donald Cape, whose job it was to make sure we didn’t export materials that would help other countries get the atom bomb. He felt it would be "overzealous" to demand safeguards to prevent Israel using the chemical in weapons production. Cape is 82 now, tall, clear-headed and living in Surrey. He told us the deal was done because "nobody suspected the Israelis hoped to manufacture nuclear weapons", but his own declassified letters from March 1959 suggest otherwise. They show, for example, that the Foreign Office knew Israel had pulled out of a deal to buy uranium from South Africa when Pretoria asked for safeguards to prevent it being used for making nuclear weapons. It also knew the CIA was warning that "the Israelis must be expected to try and establish a nuclear weapons program". Just weeks later, however, Britain started shipping heavy water direct to Israel: the first shipment left in June 1959 and the second in June 1960.

There was another problem: the Americans. There was no US-Israeli alliance in those days and Washington was determined to prevent nuclear weapons proliferation. If Britain told the Americans about the Israeli deal they would stop it. Donald Cape decided on discretion: "I would rather not tell the Americans." When Newsnight told Robert McNamara – John F Kennedy’s defense secretary – about this he was amazed. "The fact Israel was trying to develop a nuclear bomb should not have come as a surprise, but that Britain should have supplied it with heavy water was indeed a surprise to me," he said.

Kelly’s reports for the Joint Intelligence Committee (JIC) on "secret atomic activities in Israel" show that Britain’s defense and espionage establishment had no doubt about what was going on in Israel. Kelly wrote of underground galleries at the Dimona complex; there were such galleries. He correctly described the French role in the project. He identified the importance of the heavy water: with 20 tons of this material, he estimated, Israel could have a reactor capable of producing "significant quantities of plutonium". British intelligence also knew about the reprocessing facility at Dimona and stated: "The separation of plutonium can only mean that Israel intends to produce nuclear weapons." Kelly even discovered that an Israeli observer had been allowed to watch one of the first French nuclear tests in Algeria.

Kelly and his colleagues, however, found their views were being challenged. Chief of the challengers was Michael Israel Michaels (such was his middle name, literally), who was a senior official at the science ministry under Lord Hailsham during the Macmillan government, and went on to serve at the technology ministry under Benn. He was also Britain’s representative at the IAEA.

In 1961 Michaels was invited to Israel by the Israeli nuclear chief Ernst David Bergmann, and while there was given VIP treatment. He met not only Bergmann but Shimon Peres, the deputy defense minister, and David Ben-Gurion, the prime minister – the three fathers of the Israeli atomic bomb. Peter Kelly had warned his superiors that Israel might use the Michaels trip as part of a disinformation campaign to show "everything is above board", and this is what appears to have happened. Michaels’s report gave Israel the all-clear, and he handed it to Hailsham at an important moment, two days before Ben-Gurion met Macmillan at Downing Street. Kelly later took the report apart line by line and concluded by offering his own prediction that Israel might have a "deliverable warhead" by 1967.

In 1962 the Dimona reactor started operating (thanks to the heavy water Britain had delivered), yet Michaels continued to protest Israel’s innocence. The Israelis, meanwhile, were allowing the US to make inspection visits to Dimona once a year to demonstrate that it was not being used for military purposes, but Kelly saw that this, too, was a con. The tours were "heavily stage managed", he wrote in 1963, and "important developments were concealed". He was right: we now know that false walls screened parts of the plant from the inspectors.

Three years later, at the beginning of 1966, something extraordinary happened. The UK Atomic Energy Authority made what it called a "pretty harmless request" to the government: it wanted to export ten milligrams of plutonium to Israel. The Ministry of Defense strongly objected, with Defense Intelligence (Kelly’s department) arguing that the sale might have "significant military value". The Foreign Office duly blocked it, ruling: "It is HMG’s policy not to do anything which would assist Israel in the production of nuclear weapons."

Michaels was furious. He wrote "to protest strongly" against the decision, saying that small quantities of plutonium were not important and anyhow if we didn’t sell it to the Israelis someone else would. Michaels could be a bulldozer – he was short and bald, described as pugnacious and hard-headed by colleagues – and he won his battle. Eventually the Foreign Office caved in and the sale went ahead.

What is most surprising about the position adopted by Michaels is that, as the new documents show, a few years earlier he had taken the direct opposite view of the value of small quantities of plutonium. In 1961 he received a JIC report suggesting that Israel would take at least three years to make enough plutonium and then another six months to work out how to make a bomb. In the margin beside the claim about the six months he wrote: "This surely is an understatement if the Israelis have no plutonium on which to experiment in advance." Then it occurred to him that a friendly power might give Israel a sample of plutonium to speed up the process: "Perhaps the French have supplied a small quantity for experimental purposes as we did to the French in like circumstances some years ago". What this shows is that Michaels, in the full knowledge of how useful it could be for weapons development, went on to persuade the British government to sell Israel a sample of plutonium.

Today, Tony Benn can hardly believe that Michaels never referred the nuclear sales to him. Going through his diaries, Benn finds dozens of references to meetings with Michaels which show that he didn’t trust him even then. "Michaels lied to me. I learned by bitter experience that the nuclear industry lied to me again and again." Kelly believes that Michaels knew all along what Israel was doing, but since he died in 1992 we can’t ask him. According to his son Chris, after Michaels retired from the IAEA in 1971 the Israelis found him a job in London for a couple of years.

The atomic files give details of hundreds more nuclear deals with Israel. Many are small orders for compounds of uranium, beryllium and tritium, as well as other materials that can be used for both innocent and military purposes. In November 1959 someone at the Foreign Office allowed through the export of a small quantity of uranium-235 to Israel, apparently without realizing that it was a core nuclear explosive material just like plutonium.

Some materials may have been for advanced bombs. In 1966 UKAEA supplied Israel with 1.25 grams of almost pure lithium-6. When combined with deuterium, this material provides the fusion fuel for hydrogen bombs. Britain also supplied two tons of unenriched lithium, from which lithium-6 is extracted – enough for several hydrogen bombs. Deuterium, incidentally, is normally extracted from heavy water, which, of course, Britain had already shipped to Israel.

Throughout this period, Defense Intelligence repeatedly complained that Israel was the only country getting nuclear export licenses "on the basis of the meaningless phrase ‘scientific and research purposes’". The Department of Trade tried to exempt Israeli deals completely on the grounds that these were government-to-government transactions, but DIS was outraged, saying such deals were meant only for "people like most of our Nato partners who can be trusted . . . Israel however is a very different kettle of fish." In August 1966 the Israeli armed forces ordered advanced radiation dosimeters. The Foreign Office said yes and overruled the strong objections of the British MoD that they were obviously for use by troops. DIS wanted to know why Israel was always given special treatment, adding: "We feel quite strongly about all this."

Tony Benn wonders whether these deals could have gone ahead without the knowledge of the British prime ministers of the time, Macmillan, Sir Alec Douglas-Home and Wilson. The evidence is unclear. The newly declassified papers show that in 1958 a member of the board of UKAEA said he was going to refer the heavy-water deal to the authority’s executive, which reported directly to Macmillan, but there is no record that this happened. We know that Lord Hailsham learned about the heavy-water deal after it had gone through and concluded that Israel was "preparing for a weapons program".

Benn’s initial reaction to whether Wilson knew about the atomic exports to Israel was that it was "inconceivable". Then he hesitated, observing, "Harold was sympathetic to Israel," but concluded that no, he probably did not know. Benn believes that the exports were probably pushed through by civil servants working with the nuclear industry.

There was no plausible civilian use for heavy water, plutonium, U235, highly enriched lithium and many of the other materials shipped to Israel. The heavy water allowed Israel to fire up Dimona and produce the plutonium that still sits in Israel’s missile warheads today. The small sample of plutonium could have shaved months off the development time of the Israeli atomic bomb in the run-up to the Six Day War.

In a letter this year to Sir Menzies Campbell, the Foreign Office minister Kim Howells has quietly conceded Britain knew the heavy water was going to Israel. He has yet to find time to tell the IAEA that, or indeed to tell it about the plutonium or the uranium-235 or the enriched lithium. Howells and his boss, Jack Straw, are too busy telling the IAEA about the dangers of nuclear proliferation in another corner of the Middle East.

-Meirion Jones produced Michael Crick’s report for Newsnight (BBC2) on the Israeli nuclear sales, which broadcast on 9 March