Unexpected political events can have unforeseen circumstances. The surprise coronation of Theresa May as Britain’s Prime Minister is one of them. Winning power because of Cameron’s failure to persuade the British people to remain in the European Union, she took office much earlier than expected when her gaffe prone rival Andrea Leadsom stood down.

It appears that May’s sudden elevation and departure from the Home Office was the catalyst allowed some seasoned plotters unhappy for some time at Lowell Goddard’s performance as chair of the child sex abuse inquiry to act.

If Cameron had won the referendum and Theresa May was still home secretary it might well not have happened. For Theresa May could hardly accept the resignation of the third chair of a troubled inquiry within two years.

Piecing together what happened is not an exact science and not without its problems but it all points to a clever legal coup.

The most powerful figure in the inquiry apart from Goddard is Ben Emmerson, the QC to the inquiry. Nothing would have happened without his blessing and he must have been involved in her departure He is a formidable human rights lawyer, highly intelligent and an award winning barrister from a highly political chambers, Matrix, whose former partners included Cherie Blair. He also has an ego the size of The Shard and is remarkably focused to the point of being perceived as a bit of a bully.

The irony about his role in the departure of Dame Lowell is that he was the one who introduced her to the Home Office in the first place. He was the one because of his connections with the UN human rights body knew of her reputation in the human rights field .

He also rescued Theresa May at a time when two previous chairs, Dame Fiona Woolf and Baroness Butler Sloss, had to quit because of perceived conflicts of interest. At the time it seemed a brilliant move – removing any connection with the British Establishment when Establishment figures faced allegations of child sex abuse.

So what went wrong? According to different sources two things. Dame Lowell came into conflict with her own legal team about the scope and direction of the inquiry until the differences could not be resolved.

And the hard pressed secretariat became demoralised by the sheer scope and size of the different strands of the inquiry which promised to swamp their work and bury them in mounds of paper.. One source talked about absenteeism and low morale.

The decision to model the inquiry on the Australian child sex abuse investigation might have seemed a good idea at the time. But it is now clear that Australia is not England and Wales. The long running Australian inquiry has fewer numbers of people, fewer institutions and the population is much lower than England and Wales.

I suspect that one of the issues that any new chair will have to examine is how to give the inquiry more focus. This may prove to be unpopular with survivors.who are already unhappy that some institutions are not being covered and will be worried that it could be used to cover up abuse. But to have any hope of meeting a timetable the inquiry cannot be opened ended. Nor is the issue of support for survivors being addressed either.

So who will get the new job. Some see the move as a clever ploy by Ben Emmerson to take over the chair himself and appoint a new QC to the inquiry. I am not so sure he will want to be tied down for five years.

Some survivors want Michael Mansfield but this seems unlikely according to my Whitehall sources.

My money is on Dame Heather  Hallett – as being the most attractive to the PM who is bound to have a say as well Amber Rudd, the home secretary.

A grammar school girl ( though an article interviewing her suggested they did her no favours suggesting she would make a good domestic science teacher) and well grounded in the legal profession ( husband, Nigel Wilkinson is a mercantile judge and one of her sons, a barrister) she is a powerful contender.

She also showed considerable empathy as a coroner handling the inquest into the 7/7 terrorism bombings and a fair amount of guts in investigating the scandal of the Blair government giving licence to IRA killers on the run to avoid prosecution.

Whether she will want it is another matter.But whoever it is they will have to be very strong minded and an expert on English law. The first test will be the attempt by the Janner family to throw out any investigation into allegations against Greville Janner. The family are adamant that all child sex abuse survivors have fabricated the allegations against him and therefore it should not even been considered by the inquiry. This is why they want a judicial review not just to stop a ” trial “but I gather to reject any suggestion that such things ever happened.

All the survivors have been assured at a meeting with the remaining panel members ( but minus Ben Emmerson) last week that the inquiry will continue. But how it will continue will depend on the next chair.