Good Luck to You, Leo Grande

At the younger end of the British National Treasures collection, Emma Thompson is surely one of the most sparkling gems, working her way up from telly sketch shows in the Eighties to winning an Oscar for both writing and acting in the Nineties (for Sense and Sensibility and Howards End respectively), flitting between character roles (The Legend Of Barney Thomson), comedy (Late Night) and costume drama (The Remains Of The Day) with ease. She's the perfect choice then to play the older half in this two-hander pairing about retired schoolteacher Nancy, who decides to finally take control of her sex life by hiring the services of much younger sex worker Leo Grande (Daryl McCormack).

Sophie Hyde's film, written by comic Katy Brand (Glued), would be in a lot trickier territory if the genders were flipped in terms of who is hiring who in this situation and it's fair to say the script borderline labours the point of Leo emphasising how happy he is working in the escort service - although it undercuts its seriousness with some sharp humour, "I feel like Rolf Harris all of a sudden," says Nancy.

Leaving aside the political debate that this topic always generates, Thompson's performance is so perfectly pitched that it's easy to get swept up in it. Everything about Nancy is nervous, from her movements before Leo arrives to her body language once he reaches the hotel room she's booked. Her schoolteacher everyday confidence is in an internal tug-of-war with her inner feelings about her body and desires, and Thompson achieves the feat of making Nancy both stiff and twitchy simultaneously, her stress level so high you can almost hear her nerves singing. By contrast, McCormack gives Leo the relaxed air of an easygoing lap cat. Nancy has never had an orgasm, but that's not what's important to her - "I want to feel a sense of achievement," she says, and to that end, she has a list of sexy stuff she wants to give a go (something that also crops up in Lena Dunham's Sundance entry this year, Sharp Stick).

This is, like many films about the ins and outs of sex, a talky little number as Nancy reveals her fears and hopes and Leo attempts to ease her into things, offering her a drink and, rather sweetly, keeping his socks on - the sort of small detail that really makes this film tick. Inevitably, there is a slight air of the stage about this and an emotional gear change at the midway point doesn't quite feel fully earned but the actors so fully inhabit these roles that they carry you with them. Thompson in particular offers a perfect calibrated uncoiling as Nancy begins to reappraise long-held views about her body, although McCormack's subtlety shouldn't be underestimated either, as a man expected to "perform" not just in bed but in terms of the sex work persona he has carefully crafted. The result is gently satisfying - and who doesn't want that?