Concern about Britain's defences and fear of French invasion in the 1860s resulted in the construction of a string of massive forts protecting Portsmouth, the Royal Navy's premier south coast base. The forts were based on cutting edge Victorian military design and could even defend against a force attacking from inland. In the event, the threat never materialised and the forts were thereafter named, 'Palmerston's Follies', after the Prime Minister of the day. Fort Nelson has been restored and houses the Royal Armouries' artillery collection - big guns! Ramparts, tunnels and bunkers are also there to be explored.