The Lost King is a comedy-drama based on the 2012 discovery of the remains of King Richard III beneath a Leicester car park. It’s a terrific story, an unforgettable story, but a fairly forgettable film. It’s directed by Stephen Frears, stars Sally Hawkins (as Philippa Langley, the amateur enthusiast who was proved right despite being sneered at by archaeology experts), and yet it’s somehow underpowered.

True, it offers one of my favourite lines of the year – ‘Boys… Mum’s found Richard III!’ – yet it never quite springs into life. Still, it is one of those reliable British films that offers a certain amount of comfort and warmth, and faced as we are with our own winter of discontent – have you had the heating on yet?; I daren’t – perhaps we should focus on that.

The film has been written by Jeff Pope and Steve Coogan, which means that, together with Frears, it’s the same team that made Philomena. Yet this isn’t as witty or emotional or convincing.

Langley, when we first meet her, lives in Edinburgh, has two school-age sons, an estranged husband (played by Coogan) and a job in an office where she has been constantly overlooked for promotion. She suffers from chronic fatigue syndrome yet mostly appears indefatigable, which is sometimes hard to marry up. Her interest in King Richard is provoked by a local production of the Shakespeare play, after which she becomes obsessed with him, although I never fully understood why, which has to be a narrative weakness. But she can’t get him out of her head. It’s like an ear worm, yet visual. She starts seeing the king everywhere. There he is, in his cloak and crown, in her garden, or sitting at her kitchen table with his really bad hair. This is cheaply done – his get-up looks as if it came from Horrible Histories – and he’s mostly mute. Her hallucinations don’t add much and may even detract. Oh, for heaven’s sake, he’s waiting for her outside the chemist now, and is on a horse!

She is convinced that King Richard does not deserve his reputation as one of the great villains of medieval history; that he was not a hunchback who murdered his nephews to claim the throne. It’s all fake news put about by the Tudors, she believes. She joins the Richard III Society (est:1924) whose members also feel that history has not treated the king fairly. Her detailed research leads her to the car park and the society’s ‘Looking for Richard’ project funds the exhumation. It should be thrilling when the remains are discovered, but it all falls rather flat.

There’s little build-up because the film doesn’t ever find its tone, and is always ricocheting between the solemn and the sentimental. And the pacing is off, particularly in the final act which becomes less about this amazing discovery – the spine showed scoliosis which means he wouldn’t have been a hunchback but would probably have had one shoulder lower than the other – and more about the battle between Langley and the academics at Leicester University who, this says, tried to steal all the glory for themselves. (The University denies this and there has been quite a furore, if you want to look it up.)

But there are some deliciously funny moments, and the performances are excellent. Hawkins, always brilliant, plays Philippa as prickly, and stubborn, but manages to suggest that this is a character who is also somehow in search of herself. As for Coogan, there is a generosity to his performance – and he gets the best line; see above – but otherwise he doesn’t really have that much to do. Still, it’s definitely the sort of film you could do the ironing in front of. If you dare turn the iron on, that is.