Waterloo Bridge (demolished in the 1930s and replaced by the present one) was opened by the Prince Regent on 18 June 1817, the second anniverary of the Battle of Waterloo. The occasion was one of great festivity, with crowds thronging the river and neighbouring streets. Constable's painting shows the Prince embarking at Whitehall Stairs for the short river journey to the new bridge. The splendid Lord Mayor's barge is prominent on the right. Beyond the left-hand end of the bridge can be seen Somerset House, then the home of the Royal Academy, and in the centre, St Paul's. Constable was in London on that day and presumably witnessed the ceremonies, but does not appear to have thought of making a picture of them until two years later. However, he then seems to have become almost obsessed with the subject and produced a whole group of versions of it over the years up to the appearance of this one at the 1832 Royal Academy exhibition. Oddly, one of these versions is even larger than the final exhibited picture. Constable's recorded comments on the subject are extremely non-committal and the true significance of it to him remains a mystery.
Simon Wilson, Tate Gallery: An Illustrated Companion, Tate Gallery, London, revised edition 1991, p.50