The Fitzwilliam gate, located on the north eastern side of the outer curtain wall is a triple tower built after the French siege in 1216/17 when the north entrance was blocked and new entrances were created in less vulnerable locations; this gate contained a partly concealed entrance that could be used as a sallyport.

Fitzwilliam Gateway in the medieval period served as the postern and was the normal entry
point to the castle after dark. The gate consists of an upper and a lower gateway, once linked across the outer ditch by a remarkable masonry bridge roofed by a stone barrel vault that enabled the garrison to mass unseen prior to a sortie. The Fitzwilliam Gate has a beaked formation like the Norfolk Towers, but here not a modified version of a preceding gate. The exterior is apparently featureless apart from the upper loops. The base of the two side towers is battered, and there is a segmental pointed arch to the entrance passage. The steps below are of brick, on a wider stone base. Beyond the bridge, there is a tunnel through the outer rampart, this is of a C13th date but has been later modified. On the inside, a gate passage descends to the gateway, which now leads to a post-medieval bridge but had a medieval predecessor which was more elaborate and covered. There is an inner chamber above the gate and above that, a larger chamber extending forward into the tower, with five loops. (summarised from sources)

<1> English Heritage, 2014, Dover Castle Conservation Management Plan Volume 2 Gazetteer (Unpublished document). SKE52105.

<2> Johnathan Coad, 1995, English Heritage Book of Dover Castle and the Defences of Dover (Monograph). SKE52106.