Buried treasure on the island

We received an email last week from a visitor to the Island:

"Ahoy... I sailed to the island today from the isle of Battersea and stopped to water and explore. Whilst I was there I decided to bury a treasure chest with all the trinkets I've found in Deptford & New Cross during my 2 year association with the place. If it isn't discovered then I will periodically add to my stash. But here's a warning for any lubbers that intend to steal my booty - only I've got the key to the chest. splice the mainbrace, etc Pirate Paul"