Westminster Abbey's crossing tower has for centuries remained unbuilt, and numerous architects have proposed various ways of completing it since the 1250s, when work began on the tower under Henry III. A century and half later, an octagonal roof lantern resembling that of Ely Cathedral was installed instead, which was then demolished in the 16th century. Construction began again in 1724 to the design of Nicholas Hawksmoor, after first Christopher Wren had proposed a design in 1710, but stopped again in 1727. The crossing remains covered by the stub of the lantern and a 'temporary' roof.