Atlantic Wall
The Channel Islands were heavily fortified, particularly the island of Alderney which is closest to England (Jersey being the closest to France).  Hitler had decreed that one twelfth of the steel and concrete used in the Atlantic Wall go to the Channel Islands, because they were British territory.  Despite the mooting of Operation Constellation et al., the Allies bypassed the islands and did not try to liberate them when they invaded Normandy.  The islands' German garrisons did not surrender until 9 May 1945 – one day after the German armed forces on the mainland.  The German garrison on Alderney did not surrender until 16 May.