 The biggest upheaval in Harris' life was the disastrous 1809 Walcheren Expedition, in which a British force was sent to the islands of Walcheren off the Dutch coast with the aim of destroying the dykes and lock gates there to render the port of Antwerp unusable for the French navy.The expedition totally failed, as it was unable to take any of the island's major towns and bivouacked in squalid conditions during the summer, resulting in a plague of malaria and typhoid which killed over 4,000 soldiers and permanently disabled 12,000 from a force of 40,000.Harris was amongst those disabled, spending months in plague wards from which he was never expected to recover, and on at least one occasion only surviving through the extra medical care he received thanks to his financial reserves.