My friend, a prominent QC, said to me in the interval that the decision to go to war against Iraq was probably the most important this country had taken in the past one hundred years. There is no doubt that Called to Account, billed as an indictment of the Prime Minister, and devised by the Guardian journalist Richard Norton-Taylor and the director Nicolas Kent, considers this decision with diligence and trepidation.

And yet the resultant show - show trial? – is about as exciting as watching paint dry and far less enthralling than almost all of the previous Tricycle tribunals, especially those on the Scott Arms to Iraq inquiry, the Stephen Lawrence case, the Nuremberg trials and the Hutton inquiry. The difference here is that Norton-Taylor and Kent have initiated their own inquiry, aided by two real-life barristers, Philippe Sands QC for the prosecution and Julian Knowles for the defence, who interviewed witnesses earlier this year, producing 28 hours of evidence.

Boiling this down to two-and-a-half hours has not resulted in any sort of courtroom drama worthy even of Agatha Christie. You keep catching sight of the cart, but where is the bloody horse? Was the Prime Minister guilty of going to war illegally? Did he deceive the House of Commons on weapons of mass destruction? Did he manipulate arguments and evidence to justify a decision he had already taken? What is the legality of one nation state enforcing regime change in another? A great point is made of a change of heart in the attorney general, Lord Goldsmith QC, in between saying more factual grounds were needed to justify military intervention in March 2003 and giving the war legal authorisation ten days later. But what happened to make him change his mind remains in the realms of speculation.

By the end, the word “indictment” sounds rather silly, as the proceedings subside merely into a hearing and an airing of views and statistics most of us have heard time and time again. As one journalist, David Aaronovitch, said in a stage debate chaired by Jon Snow afterwards, the real issue now is not about the illegality of the war, but the catastrophe of the insurgence.

The stage is the familiar setting of office furniture, loose-leaf files, a plethora of post-its and important men in grey suits. Two journalists (Ken Drury and Jeremy Clyde) dress down in jumpers. Thomas Wheatley chips away as Phillippe Sands, while David Michaels sounds the very soul of reason as Julian Knowles, concluding that Tony Blair has done nothing that justifies condemnation. Diane Fletcher gives a brilliant vignette as Clare Short, the former cabinet minister who pours scorn on the whole process of government she was part of, while William Hoyland scores a magnificent, contrasted double of knighted witnesses - the intelligence expert Sir Murray Stuart Smith and the former defence under-secretary Sir Michael Quinlan.

But the structure of the piece is dull, with 11 witnesses examined and cross-examined one after the other. The only surprise to me was the draining of liberal-minded malevolence towards the Prime Minister as the show at least has the honesty to suggest that the case against him wouldn’t stand up in court. It certainly doesn’t in the theatre.

- Michael Coveney