Starring Ewan McGregor, Gina McKee, Eileen Atkins, and Sophie Okonedo. Unrated. Opens Friday, May 25, at the Cinemark Tinseltown

Scenes of a Sexual Nature is about sex roughly the way The Love Boat is about love. That is, certain conventions are observed in order to justify a series of playlike, mostly unconnected vignettes, each allowing actors to show what they can do, even when slumming. Only here, there's no Gopher to tie things together.

The action, which actually means "talk", takes place one sunny afternoon on Hampstead Heath, a glorious North London patch of green where people gather to get away from the city and, if this movie is to be believed, to pair off in wisecracking groups. Written and directed, respectively, by Brit-TV veterans Aschlin Ditta and Ed Blum, Scenes is essentially a comedy in search of some genuine humour, although the cast can't be faulted for trying.

Among the most memorable couplings are an uneasy picnic involving a shy bookseller (Hugh Bon ­neville) and his prickly blind date (Gina McKee), a conversation in which a gay Lothario (Ewan McGregor, easily the biggest name here) promises his long-time partner (Douglas Hodge) that he'll stop cruising if they adopt a child, and a romantic reunion for a couple (Mark Strong and Polly Walker) whose relationship is not what it seems.

There are uneasier meetings involving an absurdly harmonious yet newly divorced duo (Adrian Lester and Catherine Tate), younger marrieds (Holly Aird and Andrew Lincoln) troubled by his wandering eye, and a newly dumped woman (Sophie Okonedo) who takes out her confusion on a simple-minded bloke (Tom Hardy) foolish enough to hit on her when she's crying. Lording over them all are elderly singles (Benjamin Whitrow and Dame Eileen Atkins) who, even when they discover a fantastic secret about each other, evince all the excitement and erotic allure of the Windsors at teatime.

There are plenty of scenes here, all right. You'll have to go home for the rest.