So what if she's 37? Rafi (Thurman) is sexy, sophisticated, friendly and - thanks to a recent divorce - available. She had 23-year-old New York charmer David (Greenberg) at "Hello".

Rafi's therapist Lisa (Streep) is delighted for her, advising her to forget the age difference and let herself go. After all, 14 years makes it less of a May-to-December romance than a May-to-August Bank Holiday fling.

David's mother, on the other hand, is not happy that her boy has taken up with an older woman - and a Goyeh, no less! As a fiercely traditional control freak, she's mortified that he's dipping his toes outside the Jewish gene pool.

Mum's name is Lisa. She's a therapist. Her favourite patient is called Rafi. Oy vey.

As the overprotective mother/conflicted doctor desperate to see both son and patient happy, Streep is a joy to watch.

Prime reaches its prime during the therapy scenes. Rafi positively blooms - especially when divulging the gory details of her newly invigorated sex life - while Lisa can only gulp down her horror.

The central relationship builds convincingly. Rafi gradually allows herself to fall for David while he realises that there may be room for a little responsibility in his life. Watching his best pal throw pies in ex-girlfriends' faces is funny and all, but still...

Unfortunately, writer-director Younger (apt name) undoes all his good work by suddenly turning the urbane and previously mature David into a Harry Enfield-style teenager.

Young men, it seems, can be messy, prefer PlayStations to sex, and don't like being told what to do. Duh! It's a lazy contrivance and the story becomes forced and formulaic from that point on.

Lisa's involvement apart, their relationship is no more unusual than any other. So ultimately, Prime is not really about differences in age and faith at all. It's about doing what feels right and being happy.

The best way to achieve this would be to move on to a romantic dinner just after Dave moves in with Rafi.

Elliott Noble