Written by Lloyd George’s great-grandson, Robert, this three-hander about the Liberal Prime Minister and his relationship with his famous successor comes with bona fide credentials. Unfortunately, that close-to-the-source authenticity doesn’t reveal itself in any deep insight or unveiled secret, other than perhaps some court sexual tittle-tattle. Winston and David is a rather conventional play giving a straightforward and unchallenging history.

The third hand in the piece is Frances “Pussy” Stevenson (Alexandra Donnachie), Lloyd George’s children’s governess, his private secretary and his mistress. It is her voice we first hear as she introduces her beloved ‘LG’ and it is her perspective on the two gents’ relationship we mainly hear. So far, so good.

However, we’ve reason to suspect the words put in her mouth to be a poor reflection of reality. She speaks purely adoringly of the man 25 years her elder as if arguing for his sainthood, as if there are no further questions to be asked. On LG’s death, Churchill called him the greatest Welshman since the Tudors and for Frances that would be an understatement. Perhaps her love for him was total, perhaps he was a giant among men whose allure was inescapable – no moral judgement on age-gap relationships is being cast here. But to not properly engage with the moral ambiguity of making a mistress of your late daughter’s schoolfriend, either from her perspective or others’, seems a missed dramatic opportunity. We need more convincing on the transcendency of their love.

This superficiality is evident elsewhere too. Turning point incidents are over-flagged and under-scripted. The scene where Lloyd George loses his daughter amounts to bare statements about his grief and is accompanied by a cheap-sounding keyboard. The war, Frances tells us, with was ‘a terrible time’ after which people wanted to ‘live a bit’. It lacks the rhetorical flourishes either man could have imparted.

None of this is the fault of the actors before us. Neither Peter Swales as Churchill or Geraint Rhys as David Lloyd George attempt full on impersonations of their characters, nor do they need to. The two men’s dynamic carries without it. And Donnachie narrates well as Frances, doubles as Clemmie Churchill and even throws in a decent Michael Collins for good measure.

The play has been adapted from the author’s 2005 book and it shows, with too much attention paid to chronological veracity and not enough to characterisation. There is a story here, a nationally important one, about a cross-chamber friendship that bestrode the early 20th century and encompassed the most dramatic events in these islands’ history. But presented like this it does bear the hallmarks of a family vanity project.