We feast on political memoirs, greedily devouring their tales of what went on behind closed doors while the flashbulbs of the press were pinging outside. When seasoned with events that have sparked public outrage, their appeal is irresistible. And recently there has been no greater touchstone for the people’s distrust of government and politicians than the invasion of Iraq. It’s a shame, then, that journalist-turned-playwright Sarah Helm’s dramatisation of her life with Jonathan Powell, Tony Blair’s chief of staff leading up to and during the war, has so little meat on the bone.

Taking her lead from the “people’s princess”, anti-war Laura (Helm’s thinly-veiled avatar) opens the play by describing the man who coined the expression that launched Diana into myth as the third person in her ‘marriage’ to Nick (Powell). This sets the tone for the awkward mixture of marital strife and political melodrama that follows. High-level, secure-line phone calls are juxtaposed with the off-stage sound of children splashing in the bath; furious debates about the justification for war erupt from beneath the duvet. This cross-section of personal and public life is emphasised by a set that resembles an exploded-view floor-plan.

In different hands, this could have been gripping; after all, theatre excels at breathing life into history and giving it a human face. Here, though, we get a welter of jokes about Nick ‘cheating’ on Laura with the prime minister and a few nods to the future – Tony doesn’t know where Stockwell is (yet) and Rupert Murdoch pulls his strings – that provoke the lazy laughter of hindsight but not much else. The weighty question of Nick’s loyalty to the government in the face of growing evidence that there are no WMDs is unbalanced by excessive marital hand-wringing and tabloid-pleasing titbits about Tony’s personal habits.

Perhaps the biggest problem is that, for an insider, Helm writes so distantly. Hers is a ‘greatest hits’ Tony distilled from countless press appearances and films; a bundle of familiar tics and quirks that’s more caricature than character. It’s nothing we haven’t seen before and sometimes quite a lot less. In spite of Patrick Baladi’s best efforts in the part, the man we’re presented with bears no trace of the relentless self-conviction that led Blair to ignore the UN and invade Iraq.

There are some good points. Maxine Peake is switched-on and engaging as Laura while Lloyd Owen manages to convey the tension between Nick’s conscience and his allegiance to Tony without coming across as too much of a stooge. And they contribute a real sense of urgency and panic to a well-executed scene in a besieged Number Ten, cut off from their children by protestors as the noise of helicopters circling above makes a warzone of Downing Street.

Although the semi-fictitious Laura gives Helm some narrative latitude (for example, keeping crucial notes of important calls and being indirectly responsible for Margaret Beckett’s appointment as foreign secretary), her story feels like window dressing for the main plot. And, ultimately, this is where Loyalty falls down as a “fictionalised memoir”. Populated by major characters which simply cater to our assumptions about their real-life counterparts, it represents a missed opportunity to bring a fresh perspective to our understanding of the events that set the wheels in motion for war in Iraq. And as a piece of drama it’s hamstrung by some weak writing and the heavy-handed soap opera at its heart.

At Hampstead Theatre, 14 July to 13 August

First published by Exeunt Magazine