Comparisons are odious but rarely onerous, which is why television reviewers tend to critique programmes in pairs. The Noah's ark school of criticism is not one I'm encouraged to pursue in this column, but sometimes a coincidence of programming becomes irresistible. So it is now. On 23 February, Channel 4 began a series of documentaries on black American comedians, and on 1 March Lenny Henry, the black British comedian, returns to his roots on BBC1- the roots in question being not Africa but comedy sketches.
It is 21 years since Henry first starred with Tracey Ullman and David Copperfield in that frenetic yet cosy sketch show, Three of a Kind. His credibility was saved, some believe, by his marriage in 1984 to Dawn French. Under her influence, his comedy took a turn away from blandness towards blackness. Theophilus P Wildebeeste, that legend in his own posing pouch, was a brilliant satire on the mythic power of the black penis. ("Do you have any African in you?" he would ask a female member of the audience. "Would you like some?") Deakus, a Windrush geriatric, was a comic reinterpretation of many a community's fading elder. And so on. In the Nineties, however, Henry swerved back towards the mainstream, playing a tyrannical restaurateur in a terrible sitcom, Chef!, and the headmaster in the hopeless drama serial Hope and Glory. Race was hardly alluded to at all in either.
The opening sketch in Lenny in Pieces (Fridays, 8.35pm) seems designed to kill off all hope that Henry is returning to the subject of black Britishness. Henry, as a black loony, turns up to a page-three photo shoot and, when the photographer tells him he is underqualified on account of his sex and his breastlessness, he protests: "It's because I'm black, isn't it?" Intimidated, the snapper shoots Henry topless anyway. Ali G made this joke first, and when he did, it meant something (although no one is yet quite sure what). With Henry, it sounds simply as if he is ruling out white-on-black racism as a future topic.
In fact, amid all the programme's mediocre film parodies and jokes against middle-class archetypes, only one sketch has any potential for social satire - in which a public health inspector visits a suburban home, only to discover that the husband and children are half human and half fly. "That, madam, is an infestation," he tells the wife. "That is my husband and my children," she replies. She is white and her husband and children seem, beneath their masks, to be black, which allows room for ambiguity, but the racial possibilities quickly close down. Attitudes to miscegenation are not the subject. Henry, more's the pity, opts for Pythonesque surrealism.
And so to the odious comparisons offered by the first instalment of Kings of Black Comedy (Saturdays, 10pm, C4), a typically thorough offering from Oxford Films boasting a feast of first-class interviewees. A Funny Thing Happened to Sammy Davis Jr pursued Davis's belief that if he could make the white racists in his audience laugh, they would cease to be racist. It demonstrated how his good humour was maintained against incredible provocation. J F Kennedy disinvited him to his inauguration. The Mafia, which virtually ran Columbia Pictures, threatened him with death if he did not, within 24 hours, end his revenue-endangering affair with the actress Kim Novak and marry a black woman. He stood shoulder to shoulder with Martin Luther King, but was turned on by his own allies when, in a moment of exuberance, he publicly embraced Richard Nixon (watching the untactile president flinch was one of the funniest clips in the programme). Yet all the while, and right up to his death from cancer at 64, he was not only funny but gracious about the black predicament. "Two, four, six, eight," he tap-danced, "we don't want to integrate."
The second programme records the achievement of Richard Pryor, who mocked the whole idea of racial difference. His Seventies stage act in which he demonstrated how blacks are too cool to be bitten by snakes in the woods is one of the funniest moments of stand-up I have seen. The series ends on 9 March with an examination of how black comedy has become mainstream in America, first through the popularity of Eddie Murphy's movies and now with Chris Rock, who vented his frustration at black American culture with his famous rant: "I love black people and I hate niggers." The current kings of black comedy are four stand-ups, confusingly called The Original Kings of Comedy. They fill Madison Square Garden with black audiences, yet enjoy a big following among white people, who see in their routines access to a street culture that they are excluded from and fear.
It is not for a critic to tell an artist what his subject should be. If Lenny Henry wants to revert to his cuddly 1981 persona, that is his choice. He has done his bit to make black comedians part of the British mainstream. Let us be really charitable and call him our Sammy Davis Jr. But what we now need is a Richard Pryor or a Chris Rock to move the social commentary and the humour on. Sacha Baron Cohen has had the exclusive right to laugh at black street culture for too long. There must be other jokes to make.
Andrew Billen is a staff writer on the London Evening Standard