Galley Hill is the highest point along the coast between Eastbourne and St Leonards. It provides great views out to sea, both east and west, and as such has been used for defensive purposes since at least Napoleonic times. It was also used to watch for smuggling activity which was rife along the Sussex coastline between 1700 and 1840. A Martello Tower once stood upon it, which was the mustering point for the Blockademen before they fought smugglers in the Battle of Sidley Green in January 1828.
You can read a full transcript of the battle and the consequences to one of the smugglers by clicking here.
There is an excellent book by Mary Waugh about smuggling in Kent and Sussex, which is well worth a read.