Reading about Swan Upping, I found that in the early 20th century the ceremony began in Central London. It now starts at Sunbury-on-Thames because no swans nest on the river in Central London and few swans are seen there. This is a pity. The river landscape would be more beautiful if there were swans to be seen. The Thames, is far the most important landscape feature in Central London, and in 1496, the Venetian Ambassador’s secretary wrote that ‘it is truly a beautiful thing to behold one or two thousand tame swans upon the River Thames, as I, and also your Magnificence have seen, which are eaten by the English like ducks and geese’. We could get the swans back by feeding them, preferably with vegetable matter but a little bread would do little harm. But could the swans be persuaded to nest on floating islands, as they do on the island in Brayford Pool (Lincoln?). See webpage on The re-introduction of swans to Central London.
The Swan Island (with a willow tree) and the recently made floating islands in Brayford Pool (Lincoln)
Otherwise, this may prove to be a video of CENTRAL LONDON’S LAST SWAN
It seems you have to be careful when constructing theories about swans![ http://en.wikipedia.org/wiki/Black_swan_theory ] If the white swans become extinct we may have consider a cross breeding program with the Florida grey swan to see if we can eventually get a white one? Perhaps you could start with the black swans in Devon?