Barlett first encountered them as a boy of 16 and at first wasn't too smitten. Depicting the historical moments in which the sacraments of the Christian church were instituted and charting the journey of the body from baptism to extreme unction, the paintings are, he says, "the perfect canonical expression of ways of ordering one's life - confirmation, ordination, marriage - that I was rejecting". So why has this gay non-believer returned again and again over the past 22 years to commune with the pictures? What is the nature of the power they have over him?
These questions are the starting-point for a piece that reconnects the doubting modern mind with the old rituals and explores the emotional paradoxes thrown up.
It's not the first time that a Bartlett solo show has been triggered by visual art. A decade ago, working with the same collaborator, Robin Whitmore (who draws Bartlett in various poses during the course of The Seven Sacraments), he launched the first version of A Vision of Love Revealed in Sleep, an extraordinary "hymn" to Simeon Solomon, the gay Victorian painter who fell from grace after being arrested on an impropriety charge.
Stark naked, depilated and powdered, Bartlett mused on Solomon's fate, struck attitudes echoing the poses in the artist's erotic pictures and, with brilliant comic timing and mood-management, kept flicking between 19th-century and 1980s London. A quasi-Biblical line from the eponymous allegorical prose poem by Solomon would abruptly veer into the yob diction of the modern queer-basher; the effortful voyage in the allegory "from the agonies of Love Oppressed to the bliss of Love Revealed" would suddenly deviate into the more mundane but just as obstacle-ridden journey of a present-day homosexual trying to get home safe through a rough area of London late at night. The brave intransigence of Solomon, who refused to apologise for his sexuality and died an outcast, was held up as a model of the kind of defiance needed by gay men as they confront Aids.
In Seven Sacraments, the shifts from the past to the here-and-now give you a comparable jolt, and this technique is greatly assisted by the non- theatrical space in which Bartlett has once again chosen to place his work. A Vision of Love unfolded in the dank, draughty interior of a Butler's Wharf warehouse; to see Seven Sacraments, you have to check in at the reception desk of the Royal London Hospital on Whitechapel Road and wait to be led down neon-lit corridors into the bowels of the building, where, in the Barstead Lecture Theatre, the piece will begin.
Why a hospital? "One of the things that these paintings do," replies Bartlett, "is make a space in which you can sit down in front of life and death and love and the whole damn thing and look at it - if you like, be in the room with it. And that is something which our culture is really bad at organising these days."
Ruling out a place of worship ("for me now, the silence of a church is often empty"), he decided that a hospital, in which births and deaths are routine occurrences, would be the kind of environment best calculated to promote a focused contemplation of "the defining moments of human experience" as depicted in Poussin's paintings.
So, as I discovered when I sat in on a rehearsal last week, the piece begins as though it were going to be a brisk medical slide-lecture with Bartlett at the lectern in a white coat (the actual students have been treated that morning, I noticed, to a discourse on the dental care of disturbed patients). Bartlett makes much of the fact that, at the home of their original owner, the paintings were hung in a room by themselves, each concealed by a curtain that, for a sufficiently distinguished guest, would be drawn aside, one at a time. Those curtains and the private examination of the pictures provide a continuing rather eerie associative link with the idea of hospital curtains and medical examinations. The parallelism is kept up in other ways, too. The words of the Anglican order of baptism will be typically counterpointed by the sight of a plastic identity bracelet being clasped round the wrist of a gowned present-day patient at the Royal London Hospital.
As it develops, the piece - in which Bartlett impersonates that patient and poses as various figures in the paintings - becomes a witty and suggestive meditation on the confused feelings inspired by being at the tail-end of a tradition that you can neither subscribe to nor watch vanish without a pang. The section I saw in rehearsal certainly made me think harder about my own attitudes to baptism. We haven't had any of our three children baptised because we aren't Christians and because I don't think that you should hi-jack sacramental ceremonies, which have real meaning for some people, as the pretext for a purely social function. On the other hand, all our efforts to equip our children with the secular equivalent of godparents (a valuable relationship) have foundered because even our most enlightened friends can't be made to take the role seriously in the absence of a church christening. Given this bizarre cultural hangover, a bit of me wishes we had paid the price. Watching this show, anyone would find their equivalent cultural contradictions illuminated.
The Poussin Sacraments are full of marvellous detail, like the little boy in Extreme Unction who stands on tiptoe to get a better look at his dying father, more out of childish curiosity than concern. "He reminds me of the kid in Poltergeist," laughs Bartlett - the one whose parrot dies and is given an elaborate burial and the moment it's over, he says, "Now, about that puppy..."
Bartlett, who - it must be stressed - is in no danger of turning Christian, is adamant that the paintings "are not a closed book". There are oddities and anomalies ("one doesn't need to know whether they are intended") that give him a feeling of inclusion. "On the extreme right hand side of Marriage, there's a man in a black robe, leaning against a wall, who is not looking at anyone in the room." Say no more? Well, actually, Bartlett does say a fair bit more about (and to) this figure in the very funny sequence in the show where - "gathered together here in the sight of this congregation and in the face of considerable opposition" - he gets married to himself.
In the decade since A Vision of Love, Bartlett has come a long way in his many professions - performer, novelist, author, translator and, for the past four years, artistic director of the Lyric, Hammersmith. But there is a remarkable, imaginative unity to the body of work he has achieved with its double time-frames and its dialogues between the theatre of the past and the theatre of the present. Night After Night, for example - in which he doubled as his father in 1958 and himself at the time of this 1993 show - sprang from a fascination with the fact that the boy-meets- girl musical of the 1950s could speak to two such radically different men. Seven Sacraments, in its own very different way, also puzzles over the perverse, constituency-crossing imaginative pull of certain, less flamboyant, old rituals. It's the work of a man who would rather have full civil rights for gay couples and non-penalisation by the tax system than a white wedding, but who was "really glad" this last year that he was able to give the address at his mother's church funeral. Bartlett can be visited - in hospital - any night this weekn
London Hospital, Whitechapel Road, E1 (booking: 0181-741 2311) To 7 JulyReuse content