Candidates to become the next chief rabbi will face a "Paxman-style" grilling as the next round of interviews gets under way to succeed Lord Sacks next autumn.
A United Synagogue source said there were some "great candidates" but declined to give further details as members of the selection committee have signed confidentiality pledges to protect the identity of applicants.
The two home-grown United Synagogue contenders still thought to be in the running are Rabbi Ephraim Mirvis of Finchley Synagogue and Rabbi Harvey Belovski of Golders Green Synagogue.
A number of leading modern Orthodox American rabbis have also been the source of speculation in recent months since they were first tipped as possibles in the JC: Rabbi Jonathan Rosenblatt, senior rabbi of a large suburban community in Riverdale, New York; Rabbi Michael Broyde, a university law professor and member of the Beth Din of America; and Rabbi Meir Soloveichik, associate rabbi of Kehilath Jeshurun congregation and head of a Yeshiva University think-tank.
However, it is unclear whether all are actually in the frame.
The US source said that candidates would undergo a "gruelling" series of around six hours of sessions, which would "test their ability to speak to both a large and small group of people".
They will also experience a "Paxman-style interview" on a "controversial subject", alluding to the tenacious BBC2 Newsnight presenter, conducted by the former United Synagogue president Simon Hochhauser.
While the selection committee had hoped ideally to appoint their man a year ahead of Lord Sacks's retirement in September 2013, the US source said: "We are not being driven by a timetable, but by finding the right candidate."
The door also remained open to late entrants. "If somebody fantastic comes along, we are going to have to talk to them," the source said.
Rabbi Rosenblatt, who has been at Riverdale since 1985 and is in his 50s, was the centre of interest this week, arriving in the UK for a wedding. He was widely expected to be meeting the search committee.
One British rabbi said that he was the "outstanding candidate" from abroad with "all the required talents to bring to this particular office".
Rabbi Rosenblatt, he said, had a track record as a mentor of other rabbis and would take a strong interest in grassroots congregational development.
With a doctorate in British literature, he "probably gets the British more than most British get themselves," he said.
"Although he hasn't produced a lot of written stuff because he has been such a devoted community figure, he can write as well as Rabbi Sacks. He is an orator of the first order."
Rabbi Broyde visited in May. Rabbi Soloveichik is due here next week as guest speaker at the Chief Rabbi's pre-High Holy Day conference for rabbis - as Rabbi Broyde was in 2009 – although he has not revealed whether he is interested in the role of chief rabbi at the present time. One senior educational Orthodox figure doubted whether Rabbi Soloveichik had even applied.
According to one rabbi, the selection committee has yet to make up their minds on what focus they wanted for the job, toying with three models for the post.
One would be to follow in the footsteps of Lord Sacks as a public intellectual and voice of Judaism to the outside world; the second would be an internal governor of the US, setting religious policy and overseeing the London Beth Din; and the third would be a "rabbis' rabbi", a spiritual mentor to the ministry.