The 15th and 16th centuries saw a small number of British castles develop into still grander structures, often drawing on the Renaissance views on architecture that were increasing in popularity on the continent. Tower keeps, large solid keeps used for private accommodation, probably inspired by those in France had started to appear in the 14th century at Dudley and Warkworth. In the 15th century the fashion spread with the creation of very expensive, French-influenced palatial castles featuring complex tower keeps at Wardour, Tattershall and Raglan Castle. In central and eastern England castles began to be built in brick, with Caister, Kirby Muxloe and Tattershall forming examples of this new style. North of the border the construction of Holyrood Great Tower between 1528 and 1532 picked up on this English tradition, but incorporated additional French influences to produce a highly secure but comfortable castle, guarded by a gun park.