Lostwithiel is in the Deanery and Hundred of Powder. It is bounded on the East by St Winnow and on the North, South and West by Lanlivery, with which parish it is closely identified. Lostwithiel town is situated at the head of the estuary of the River Fowey to which point it is tidal. Lostwithiel was once the capital of Cornwall. Restormel Castle, about a mile away, was rebuilt by the Black Prince, the first Duke of Cornwall, but after his death the castle and town decayed and the river silted up.