Philip Hensher: This picture is a work of art

The artist Alison Jackson has made a considerable name for herself with photographic tableaux of celebrities and public figures in undignified and private, but altogether credible, positions. Lady Thatcher and Lord Archer sit at a table, behind bars; Prince William tries on the crown; Cherie Blair grips her husband's bum, unseen by a phalanx of photographers; Sven-Goran Eriksson mutters to Wayne Rooney, lying in an oxygen tent.

They are highly amusing and ingenious inventions, staged by look- alikes. Despite their obvious satirical load, they have a serious intent. They dwell on the distinction between the private and the public, and, in the public arena, the difference between what is known to be the case and what is presented to us in visual form. Beneath the chaotic and disordered surface of reality lie the ordered ranks of artistic archetypes; or, alternatively, underneath the controlled images of public figures, art can reveal the messy reality of the individually human.

Art is not always to be found in the most obvious places, and, looking at the extraordinary photographs of John Prescott playing croquet at the weekend, one found oneself mesmerised as if by a highly considered, symbolic composition. They are taken by Gary Trotter, to whom I take my hat off. There are two principal photographs. In the first, a neatly horizontal arrangement of six figures is ordered in four groups, a solitary figure and a pair, another solitary and another pair. The figure at the left closes off the composition with an upraised arm; Prescott himself provides a grand diagonal, included within the group, the croquet mallet continuing the line of his belly. It is an image of egalitarian harmony, pastoral charm.

In the other one, two figures stand respectfully to either side of Prescott, who is awkwardly bent over his mallet. There, the meaning is plain; it is of someone playing a game, not very well, who nevertheless is going to be allowed to win. As an image of arrogance, of timewasting, it could hardly be bettered.

The genius in Trotter's photography, however, was in the choice of croquet as the site of the drama. Since the reshuffle, everybody has come to the conclusion that Prescott has very little to do, and we've been waiting, surely, for the defining image of Prescott as a member of the contemptuously idle rich. Croquet, with its aroma of Edwardian leisure, is surely perfect for the purpose; perfect, too, the notoriously petty-minded nature of the game, in which a successful player will boot anyone in his way to kingdom come.

At first, I didn't appreciate the genius of Trotter's choice of croquet. Surely, one thought, a game of darts might have been more in keeping? But the cleverness of the choice is undeniable. Croquet is, of course, a game with snobbish overtones - so much so that it is pronounced two entirely different ways: many a social climber has been confused by le gratin talking about "croaky".

Prescott's entourage, from their defiantly non-county clothes, look to be of the "cro-kay" school. He, on the other hand, is in the universal upper-middle-class summer weekend uniform of Brooks Brothers shirt and pale chinos. And, to articulate Prescott's image, nothing better could be devised than this aspirational uniform, this absurdly aspirational game. Ken Livingstone has said that a lot of the criticism of Prescott is directed at his social class. That's certainly true; but what this photograph expresses is the feeling that he is a rich man who maintains, for his own purposes, the appearance of an ordinary member of the working classes. Prescott, this photograph says, might choose to play darts and thump strangers in public, but in private, he prefers croquet.

Since the beginning of Western history, art has demonstrated large public truths through the depiction of sporting contests. It is almost axiomatic in Jane Austen that a character's conduct at the card table will show their true character. Throughout the Empire, games of cricket were used in fiction to demonstrate where power, or strength of character, truly lay.

Trotter's photograph of Prescott's playing a game of croquet while he was supposed to be running the country falls into the same artistic category as Satyajit Ray's The Chess Players as an image of abdicated power, and it's difficult to see how conscious arrangement could improve on it. The real talent, surely, is the way it takes a treasured national myth, of Drake nonchalantly going on playing bowls on Plymouth Hoe, and burlesques it. What is revealed by this symbolic image is not casual confidence, but, apparently, idle diversion. No conscious artist could invest so much neat political meaning in an image; no labour of the imagination, one feels, could have found so perfect a means of expressing a political argument.