n The defining moment in Malcolm McDowell's screen career comes fairly early on: at the end of Lindsay Anderson's surreal satire O Lucky Man!, when McDowell, having suffered a lifetime of incredible reverses of fortune, wanders into an audition in a London warehouse. He's down on his luck; he's enjoyed the sweetest fruits and the bitterest dregs life has to offer; and now he finds himself penniless, resigned to the absurdity of his life, looking for something - anything - to give him a new direction.

n Anderson himself plays the director looking for someone who can smile despite his troubles; he glimpses McDowell, takes him up on stage and tells him to smile. McDowell asks: ''What is there to smile about?'' Anderson slaps him and commands him to smile. McDowell refuses, repeats his question. Anderson slaps his face again, harder: ''Smile!'' And then something beautiful happens; McDowell's eyes glow with a kind of lust, give an intimation of the secret knowledge he's carrying within himself, and he smiles - gloating, vulpine, exuberant. He's down but not out; he's hungry for more of the punishment that comes with being human. It's one of the greatest scenes in film, and no-one but McDowell could have carried it off.

n McDowell's handsome, leonine face and air of arrogance and insolence were intoxicating, and were perfect for his first two major roles: as the schoolboy revolutionary burning down the Establishment in Anderson's If . . . , and, infamously, as Alex, that connoisseur of rape, ultraviolence, and Beethoven, in Stanley Kubrick's A Clockwork Orange. These characters were gleefully amoral, in love with violence, and, for all their sociopathy, they were played as modern heroes, Dionysians in a world feeble and mediocre.

n Before this he'd been a spear-carrier in the RSC for 18 months, before that in rep on the Isle of Wight, before that a coffee salesman in Yorkshire (which experience was to provide him with the kernel that became O Lucky Man!). Few actors can match McDowell's record of having worked in three such stunning, crucially important films so early in their careers - and few have suffered as profound a decline. There have been flashes of greatness: comedic, as Flashman; with Anderson again in Britannia Hospital; in Paul Schrader's interesting remake of Cat People (on BBC2 this Sunday night); but he's appeared in a lot of shoddy, inconsequential films: tonight's Buy and Cell, is, I fear, one of the latter. The part of the Soho pornographer Bernie Barratt in Our Friends in the North hinted at how he can still play maliciousness and viciousness like no-one else, but for the moment, Malcolm McDowell's

best work lies in the past.

Malcolm McDowell stars in Buy And Cell. (Scottish, 1.10am)

Kevin McCardle