There are records of the Thames freezing over as far back as CE 250. The piers of old London Bridge were broad and close together, meaning that they could get easily blocked creating a dam which would slow the water enough to allow it to freeze in cold winters. The Thames embankments have meant that the river now flows faster than it did previously. This, together with the wider arches under London Bridge, and of course, global warming, mean that we should not expect to enjoy any Frost Fairs ourselves.
Diamond Geezer gives a time-line of the various Frost Fairs 1434 - 1814. Our image shows a painting of the 1684 Frost Fair.