Though the main construction period for the Casemate level tunnels at Dover castle was between 1797 and 1798 a number of additions and alterations were made to facilitate its continued use throughout the 19th century and during both World Wars.

These alterations include a long, north south aligned tunnel (W tunnel) on the western side of the eastern block of tunnels (just to the west of block X) which was constructed in November 1942. A tunnel on the far north eastern end of the complex which was constructed in 1870 and then extended in 1941 and again in 1944, and another north/south aligned tunnel connecting the northern half of block D, to the long east west corridor which connects the two sets of blocks on the northern side, which was constructed in 1940-1941. (1-2)

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 English Heritage, 2014, Dover Castle Conservation Management Plan Volume 2 Gazetteer (Unpublished document).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