ships created a new risk that the French might successfully attack along the south coast, and fears grew of a conflict in the early 1850s. Southsea Castle and St Mawes were extended with new gun batteries, Pendennis was reequipped with heavier guns and Hurst was extensively redeveloped. There were discussions about rearming Calshot, but these were rejected, in part due to concerns about the suitability of the 16th-century walls in modern warfare. The Crimean War sparked a fresh invasion scare and in 1855 the south coast of England was refortified. New guns were installed at St Catherine's and Yarmouth in 1855. The remains of the West Blockhouse were destroyed by a new fortification, the West Blockhouse Fort, designed to deal with the French threat. Fresh worries about France, combined with the development of rifled cannon and iron-clad warships, led to the Royal Commission on the Defence of the United Kingdom being established in 1859, and expressing fears about the security of the south coast. In response, Sandgate was re-equipped with heavier guns in 1859, and extensive work was carried out on Southsea. Hurst was fitted with two huge batteries of heavy rifled breech-loading guns, protected by iron armour-plate, intended for use against fast-moving enemy warships. Tilbury Blockhouse was destroyed to make way for heavier guns at the fort after 1868. Portland was readopted by army as a garrison base in 1869 in response to fears of an invasion, but it was not rearmed. A fresh wave of concerns about France followed in the 1880s, accompanied by the introduction of still more powerful naval artillery and fast warships and torpedo boats, resulting in a fresh wave of modernisation. An electronically operated minefield was laid across Carrick Roads in 1885, jointly controlled from St Mawes and Pendennis. New, quick-firing guns were installed at Hurst to enable the castle to engage the newer vessels. Calshot was brought back into service as a coastal fort, with a new battery of quick-firing guns protecting a boom across the estuary. The original 16th-century parts of fortifications such as Southsea and Calshot were too small and unsuitable for modern weapons, however, and were instead used for mounting searchlights, range and direction finding; in some cases their fabric was left to slowly decline. Some other sites were no longer considered viable at all. West Cowes was decommissioned in 1854 and became the club house of the Royal Yacht