The British government is now “far more likely” to side with Israel and President Trump against Iran following the meeting this week between Prime Minister Theresa May and Benjamin Netanyahu, a security expert with strong Whitehall ties has confirmed to the JC.

The Israeli Prime Minister arrived at Downing Street on Wednesday for crunch talks aimed at convincing Mrs May that the Iranian nuclear deal is on the point of collapse and that a fresh plan is needed to stop Iran restarting its uranium enrichment programme.

In her statement before the meeting, Mrs May appeared to suggest she was not willing to follow the lead of Donald Trump and pull out of the Joint Comprehensive Plan of Action (JCPOA) on Iran — which eased sanctions on Tehran in return for dropping its bid to develop nuclear weapons.

Reaffirming the UK’s commitment to the deal she said: “Along with France and Germany the UK continues to believe that is the best route to preventing Iran from getting a nuclear weapon”.

But the wording was careful. In a sign of the impact of Mr Netanyahu’s decision to allow a cache of Israeli intelligence files seized from a Tehran warehouse in January to be shown to British security services this week, Mrs May added: “We will remain committed to it as long as Iran meets its obligations.

“But we do recognise that there are other issues that need to be addressed in relation to Iran — its destabilising regional activity in countries like Syria and Yemen and also the proliferation of ballistic missiles.”

Posing for photographs at the start of the Downing Street meeting, Mr Netanyahu said he was determined to stop Tehran from producing a nuclear weapon and would discuss “how to roll back Iran’s aggression in the region”.

He said to Mrs May: “I think we can find ways to work together to achieve both goals.”

Confirming that the files handed over to Britain by Mossad had included damning new evidence that showed Iran had violated the origin of the 2015 accord, when Iran claimed it had never had any nuclear weapons programme — including an Iranian memo formally handing responsibility for the production of weapons-grade enriched uranium to the Iranian defence ministry — the Whitehall source told the JC: “The files seized by the Israelis are damning evidence of Iran’s duplicity and they have had a real impact on the UK position.

“The government is unlikely to make this public but it if it comes to a stand-off between the US and EU over Iran, we are now far more likely to be on the US side.”

After the meeting, an Israeli source said Mossad would share further material from the cache of more than 100,000 documents in a further effort to persuade the British government to shift on the nuclear deal.

“Everybody in that room in Downing Street knows the deal is not a good one,” said the source.

Asked if the Mr Netanyahu was happy at the end of Wednesday’s meetings, the source said: “I believe so.”

Mr Netanyahu had pushed the same hard line on Iran throughout his trip to Europe this week — with Germany’s Chancellor Angela Merkel in Berlin, and French President Emmanuel Macron in Paris.

The Israeli pressure is designed not only to back President Trump’s decision to pull out of the deal but also to force European firms to disinvest from Iran.

Sources on Wednesday evening said Mr Netanyahu was left with “hope and belief” that the best chance of real success in breaking continued support for the Iranian deal was with Britain.

“Britain has looked more closely at this cache of documents than some,” another source close to the government told the JC.

France and Germany have viewed the lifting of sanctions against Iran as an opportunity to pursue lucrative commercial interests. They argue that modernisation of Iran will help to produce a modern, moderate leadership in Tehran.

But one Israeli diplomat insisted: “There’s certainly a feeling that Britain is currently the weakest link in the European resistance to Trump’s policy.

“With Brexit, Theresa May cannot afford to anger Trump, as Britain needs a trade deal with the US.

“Neither can the banks and insurance companies of the City of London allow itself to be part of any EU attempt to save the Iran deal by financing deals with Iran. It simply can’t cross the Americans.”

Away from the issue of Iran which dominated the Downing Street talks, Mrs May expressed her concern about the deaths of protesters on the Gaza border last month, when the Israeli military used live ammunition.

Mr Netanyahu has insisted the protests were driven by Hamas and the response was aimed at minimising causalities.

After the meeting with Mrs May, Mr Netanyahu sat down with Foreign Secretary Boris Johnson.