At that time British land-based defences were woefully inadequate to defend against an invasion as Great Britain had always relied on the Royal Navy for its defence. To prepare for invasion in 1794 British Parliament purchased a large piece of land at Shorncliffe, the obvious place for initial fortifications to be built as it was just 20 miles away from the French coast, so close, in fact, that the locals could see the smoke from the camp fires of Napoleon's waiting army. Later further defences were added to the Kent Coast including the 28-mile-long Royal Military Canal, started in October 1804 and finished in June 1805, which stretches from Cliffend to Seabrook. Also Martello Towers were built between 1805 and 1808 to bolster the defences.