Think of a swan; think graceful, elegant, serene, and dignified. Visualise a life unhurried, unharried, unflapping, excepting occasional 747-rivalling take-offs.

Last week I saw swans in a context quite different from the placid patrolling of a park lake or magisterially routing the mallards when bread appears.

I was invited to join the Press to observe the Queen's Swan Markers and Wardens Swan-upping between Marlow and Henley. There I watched the annual ceremonial census in perfect weather, after the team had got a thorough dousing the day before.

A flotilla, including a Brazilian TV crew (what are Brazilians to think of this strange British spectacle?), was cheered off from The Compleat Angler by children from Bisham, Foxes Piece and Cadmore End.

Anyone can keep swans, but only the monarch, or one of two ancient livery companies, the Vintners or the Dyers, can own them.

From medieval days, when swans were an ever-fresh source of sophisticated protein for the nobility, their ownership has been jealously guarded.

Annually, swans with young are tracked and, at the cry of "Swan up!", skilfully encircled by boats manned by uniformed officers, caught, upped, and registered. The boats of the two royalty companies have two rowers each, dressed mainly in black, while the Queen's boat has three rowers in glorious scarlet and white. Each boat carries its respective Marker. Livery companies, now mainly ceremonial, retain some practical function. The Vintners include the maintenance of wine standards among their modern responsibilities.

When the whole swan family, parents and cygnets, is carefully trapped against the river bank, the 'Uppers' quickly and deftly overpower and land them, with surprisingly little struggle. Adults' wings are skilfully tied together with cord, as are the legs of all birds. This removes risk of self-inflicted injury and, until they are released, there is no struggle, no apparent stress. They quickly become docile and placid, if slightly less dignified than on the water, with only an occasional hiss from a cob to assert his continued authority. They take little notice of humans who can touch unimaginably soft plumage.

A few feathers are lost in the capture, and I over-hear some mumblings about cruelty. But the parent birds are moulting now. They do it serially, ensuring that one bird always remains fit and capable while the cygnets need protection. However, it seemed worth having a word with Professor Christopher Perrins of Oxford University's Edward Grey Institute of Field Ornithology. As the Queen's Swan Warden, he continuously monitors the birds' welfare. "If the chance to remove fish hooks from gullets or take sick birds away for life-saving treatment is cruel, then I suppose that's how you must judge it", is his response. "I've knelt over an adult, ringing its leg at one end, when the other end has been busily devouring a loaf of bread - not an obvious sign of stress."

Indeed, the birds are totally peaceful while they are weighed, measured, given a health check, and then have their ownership decided. If either parent wears the Queen's ring, or, rarely, if both parents are unmarked, then the cygnets are the Crown's, though Her Majesty, graciously, usually cedes half to be divided between the two Livery companies.

The Swan Markers emphasised that the involvement of the children we met up with from time to time along the river was more important than the cataloguing of the birds. Young people with a sense of value and involvement will ensure the swans' future welfare more surely than all the scientific recordings; vandal attacks will become unthinkable.

This year's count showed attacks and weather had affected breeding much less than feared. Exceptional flood patterns had been expected to exact a worse toll. Early nesters had their eggs destroyed as the waters rose, while later breeders, building high as the result of the flood water persisting, were then left high and dry by the receding river, thus unusually vulnerable to predators. While down on last year's exceptional breeding season, numbers of cygnets are likely to be around the annual average.

Professor Perrins remarked how birds suffer from entanglement with fishing tackle, or swallowing lead weights. Some of these are still used illegally, while the two smallest grades of weight can still be made from lead, since there is no practical substitute. "Nonsense, of course!", pronounces the Professor, "there's a perfectly adequate alternative. Denser than lead, not toxic, it is much less likely to be lost by fishermen it's called gold."

Finally restored to the water, maybe a quarter of an hour after being duped into the bank, the swans swim off, adults rising on the water with out-stretched wings, all twitching tails in a triumphal display to their new human owners. My final conviction is that anyone can help to "keep" swans but, noone really "owns" them.