Mersea is one of the UK's larger tidal islands, as well as its easternmost. It's located just off the coast of Essex, about an hour's drive east and north of London. Once a seaside retreat for Britain's Roman overlords and later a hiding spot for pirates, the island was heavily fortified during the World Wars for fear of it being used as an invasion route. Its population has grown considerably since then as it's become somewhat of a bedroom suburb to London. You can check it out from above in this drone video by binesh.