A meeting last year at the Ministry of Defence between Defence Secretary Liam Fox and the incoming UK ambassador to Israel, Matthew Gould, will form a key part of the inquiry into the relationship between Dr Fox and his best man, Adam Werritty.
Questions will also be raised about a dinner Mr Werritty helped arrange at the Herzliya Conference in February this year.
The JC can reveal that Mr Werritty was considered to be Dr Fox's "chief of staff" by some of those who dealt with him, although he had no official job within the MoD.
Dr Fox was forced to admit this week that his friend should not have been present at a sensitive meeting at the MoD with the ambassador-elect.
The Defence Secretary is known as a champion of Israel within the government. Speaking at the Herzliya Conference in February, which Mr Werritty also attended, he urged tougher sanctions against Iran, Mr Werritty's area of expertise.
An interim report into the affair from MoD Permanent Secretary Ursula Brennan was presented to the Prime Minister on Monday. In a letter to the Cabinet Secretary Sir Gus O'Donnell, Ms Brennan noted that other people had been present in only four of the 22 occasions on which Mr Werritty and Dr Fox had met at the MoD. Three of those were on the subject of Sri Lanka but the fourth concerned Israel.
"The fourth was an occasion when Mr Werritty was present during a meeting with the then forthcoming ambassador to Israel," she wrote. "Dr Fox acknowledges that it was not appropriate for Mr Werritty to have attended such a meeting at the MoD."
The next stage of the inquiry will look into all the meetings in closer detail. Mr Gould was appointed to his post in December 2009, but did not take it up until last autumn. According to diary entries released by the MoD on Monday, the crucial meeting with Mr Gould took place on September 1 2010 with an FCO official present, as well as Mr Werrity.
The diary also has an entry for the Herzliya conference on February 6-7 2011 which states: "Adam Werritty helped to arrange and attended a dinner with political figures which SofS [Secretary of State] and HMA [Her Majesty's Ambassador] Tel Aviv attended".
Lee Petar, a former director of communications at Israel lobby group Bicom, has found himself at the centre of the storm around Mr Werritty. Mr Petar's PR company, Tetra Strategy, was employed by Harvey Boulter, the British businessman whose revelations have caused so much embarrassment to the Defence Secretary.
Mr Boulter's company, the Porton Group, employed Tetra to advise them on a claim against American company 3M. A statement issued by Tetra on Monday said: "The case concerned the development of new MRSA testing technology developed by the MoD. Tetra introduced its client to Adam Werritty in March 2011, widely believed at the time to be an official adviser to Dr Liam Fox. The purpose of the introduction was to brief the MoD on the litigation."
Tetra Strategy counts among its clients the investment company Tamares, owned by Bicom chairman Poju Zabludowicz.
The JC understands that Bicom paid for Mr Werritty to visit a previous Herzliya Conference,
while he was working for Dr Fox in opposition.