Christmas, 1669. In the grip of the coldest winter for years, the River Thames is frozen from bank to bank and London celebrates with a traditional frost fair held on its broad back. Revellers come from far and wide to enjoy the spectacle. Among the throng is ambitious young architect Christopher Redmayne. By chance he meets a good friend, Constable Jonathan Bale, attending with his family. As the adults talk, Bale's sons skate around them. But their...