In July 1809, with the Dutch coast 'a pistol held at the head of England', the largest British expeditionary force ever assembled, over 40,000 men and around 600 ships, weighed anchor off the Kent coast and sailed for the island of Walcheren in the Scheldt estuary.
After an initial success, the expedition stalled and as the lethargic military commander, Lord Chatham, was at loggerheads with the opinionated senior naval commander, Sir Richard Strachan, troops were dying of a mysterious disease termed 'Walcheren fever'.
Almost all the campaign's 4,000 dead were victims of disease.
The Scheldt was evacuated and the return home was followed by a scandalous Parliamentary Enquiry.
Walcheren fever cast an even longer shadow. Six months later 11,000 men were still registered sick.
In 1812, Wellington complained that the constitution of his troops was 'much shaken with Walcheren'.