Inside the court of King Tony

There may never be another inside account quite like it: the first credible indications of how Rupert Murdoch encouraged Tony Blair to go to war; the most detailed version yet of one of those Iraq telephone conversations between President George W Bush and the British Prime Minister in the run up to the Iraq invasion; and a graphic if more fanciful portrayal of panic rising much later in Downing Street as the bankability of a key intelligence source for the presumed existence of Saddam's weapons of mass destruction begins to crumble.

Sarah Helm's play Loyalty, which opened in London this week, does not scoop the Chilcot inquiry into the war, due later this year. But it may tell us more about the atmosphere in which the invasion of Iraq was launched and sustained than Chilcot ever will. And all from the extraordinary vantage point of the wife of Tony Blair's chief of staff Jonathan Powell, his closest aide throughout his premiership. A former Independent journalist who had worked in the Middle East, she took her two children to join the million-strong march against the imminent war which Mr Powell was professionally engaged almost non-stop, at Mr Blair's side, in prosecuting.

She says her play is a "work of fiction" but has also acknowledged it was "drawn from real events". As a whole the play is not a historical record, especially since the final denouement in the second half is the fruit of dramatic imagination. But it is unlikely that the call from Rupert Murdoch in which she depicts the couple, Nick and Laura (based on herself and Mr Powell) listening in on – in her case notebook in hand – is entirely made up. Even if a composite, it has a distinct ring of authenticity, reinforced by the Cabinet Office's admission in July 2007, shortly after Mr Blair left office, that the News Corp chairman made three separate phone calls during the March run-up to the invasion.

The then all-powerful seeming Mr Murdoch announces to Mr Blair that he has been speaking to the US Defence Secretary Donald Rumsfeld who he says is "dead set" on going ahead with the war. Mr Murdoch tells Mr Blair that "Don's boys need Diego Garcia" – the British Indian Ocean Territory which is also home to a major US military base.

When Mr Blair replies that the UK government has already been "in discussion with them on that", Mr Murdoch repeats that that Mr Rumsfeld "needs" Diego Garcia and adds: "He'll go without it, Tony, make no mistake, but he'd like to have it. So it's your call. We'll be with you. Editors have been told." After a pause Mr Murdoch concludes: "It's the right decision, Tony. Believe me."

In what is understood to be a near verbatim account of an early March Bush-Blair phone call about the (as it would quickly turn out) doomed efforts to secure a second UN resolution justifying the war the two leaders congratulate each other on their "courage", with the US President saying he is "just ready to kick ass". They both express frustration at the opposition to the war of Jacques Chirac, whose behaviour, Mr Blair tells the US president, is "absurd". After Mr Blair pleads – in deferential terms – for another few days before the issue of the draft UN resolution, there is a pregnant exchange apparently referring to what would later become the discredited source "Curveball" – the Iraqi who admitted earlier this year that he had "fabricated" the story he gave to the German intelligence agency BND.

BUSH: "But you know the Germans have got some really good new stuff showing he has those biological weapons. You've seen that right?"

BLAIR: "Well, just heard something today. The Germans have a new source. Yeah. Sounded really convincing."

BUSH: "Y'know, the German stuff shows that son of a bitch is really ready to offload. No doubts now Tony."

BLAIR: "No. Right. I got that too - from Berlin. Yeah. Great stuff."

Blair then affirms that the UN weapons inspections chief Hans Blix cannot be allowed a veto and Bush quickly interjects that Mr Blix is a "no count". Near the end of the call, the US President again congratulates Mr Blair, saying: "I'll try and put it in your comfort zone Tony. We don't want regime change in London before we have it Iraq now do we?"

Before they say goodbye Blair tries to reintroduce what he always hoped would be the quid pro quo for his support in Iraq. "Oh George, just one thing, and I know you think I keep banging on about this, but on the road map thing... if you can give us anything on Israel-Palestine it..."

BUSH: "Oh yeah, sure, but gotta hop now. So catch you later." Pause.

BLAIR: "Yeah, bye George."

BUSH: "Oh and Tony. Don't forget – cojones."

At another point Blair admits to Bush he fears the war could be his "epitaph". In his programme note for the play, Sir Sherard Cowper-Coles, who was principle private secretary to Robin Cook when Cook resigned over the war, says the play is at bottom "a love story" about Nick and Laura, one of "how two individuals, deeply committed to each other, but with profoundly different views on the central issue of the time, somehow keep going through it all."

That's true.

But more politically it is also a telling indictment of how a Prime Minister committed to one highly controversial military objective – regime change in Iraq – tragically strained every sinew to use another one to persuade the British people and parliament to back the war: the eradication of weapons of mass destruction which in the end didn't even exist, let alone threaten the security of the UK.