In the mid-19th century it was French activity that stirred the British Government into action. France had started a scheme of naval reconstruction, with new ironclad steam powered warships, whilst also fortifying several channel ports. This was enough to trigger another invasion scare, prompting Lord Palmerston, the then Prime Minister, to establish a Royal Commission to study the question of coastal defence. The commission reported in 1860 and concerned itself mainly with the defence of naval harbours. This resulted in a vast scheme of coastal defence construction along the south coast and Thames Estuary. Although Newhaven was not yet a naval port, the decision was taken to provide it with a fort. After some quibbling over cost estimates, Lieutenant J.C Ardagh of the Royal Engineers was placed in charge of design and construction. Preliminary work started in 1862, with work finishing in 1871. As the first troops moved in, their task was to prepare the site for reception of new guns from Woolwich.