The programme to develop a steam-powered, iron hulled fleet, accelerated plans for the extension of Chatham Dockyard. In 1863 work started on newly enclosed mudflats to the north of the yard which had been acquired by the Navy in 1855. The whole works, including three non-tidal basins with four dry docks took until 1885 to complete, with much of the labour provided by over 1000 convicts housed in a prison built nearby. New buildings erected alongside the basins included a factory, boilershop and numerous machine shops.
