British cinema audiences haven’t seen much of Adèle Exarchopoulos since her breakthrough as co-star and titular co-winner of the Palme d’Or at Cannes for Blue Is the Warmest Colour (2013). Sadly, her new film is a Prisoner Cell Block H piece of jail-love sauciness and a weirdly sanitised fictional version of a real-life case. In 2012, French prison governor Florent Gonçalves was jailed for having an affair with an inmate, Emma Arbabzadeh; she was serving time for luring a Jewish man to his death at the hands of a racist gang. This movie is loosely based on Gonçalves’s own book about the case and he is credited as a producer. But the obvious question of Emma’s modus operandi and whether this prisoner was compulsively manipulative are primly ignored in favour of a solemnly simplified love story – a kind of Abelard and Heloise sexy-weepie. Exarchopoulos plays Anna, a young woman who in prison for … we don’t know. It is not mentioned. Guillaume Gallienne is Jean, the hunky and caring prison governor who is menopausally approaching his 40th birthday. Anna and Jean fall in love and it ends badly, of course. Exarchopoulos has natural charisma, but her character is bland because of this film’s outright refusal to talk about her backstory.