Construction was commenced at Seabrook, Kent, near Hythe in Kent on 30 October 1804.
The canal was completed in April 1809 at a total cost of £234,000. The canal was
built as a third line of defence against Napoleon, after the British Royal Navy patrolling
the English Channel and the line of 74 Martello Towers built along the south coast.
Romney Marsh was considered to be a likely point of invasion for Napoleon's Army,
particularly during the period of the Third Coalition.
However, the planned invasion by Napoleon never eventuated and the threat of a French
invasion was greatly diminished following the Battle of Trafalgar in October 1805.
The canal was still a long way from completion at this point and the cost of its
construction was becoming politically difficult for the government.