These coins were struck to commemorate the Festival of Britain.
The Festival of Britain was a national exhibition which both commemorated the centenary of the Great Exhibition of 1851 and was to promote improvements in design for the post-war rebuilding of the country. The official opening was on 3 May 1951 but the exhibition was not in a single place, there were components around the country as well as touring exhibitions. The principal exhibition sites were the South Bank, London on the Thames near Waterloo Station; Poplar, East London (Architecture), Battersea Park (Festival Gardens), South Kensington (Science) and Kelvin Hall, Glasgow (Industrial Power).
All coins are "Prooflike" or "Proof".