Thames House is an office building in Millbank, London, on the north bank of the River Thames adjacent to Lambeth Bridge. Originally used as offices by Imperial Chemical Industries (ICI), it has served as the headquarters of the United Kingdom's internal Security Service (commonly known as MI5) since December 1994. It also served as the London headquarters of the Northern Ireland Office (NIO) until March 2013. History The building was constructed in 1929–30 by John Mowlem & Co on riverside land cleared after the disastrous 1928 Thames flood severely damaged run-down residential properties. It was built to designs by Sir Frank Baines, of the Government's Office of Works. It is of design uniform with but not identical to Imperial Chemical House which is opposite it on the north side of Horseferry Road; while Imperial Chemical House remained exclusively for ICI until its exit, Thames House had additional tenants alongside ICI throughout history, including the London headquarters of International Nickel Ltd. Baines's design owes much to the 'Imperial Neoclassical' tradition of Sir Edwin Lutyens and deliberately ties in with the Imperial design of Lambeth Bridge when it was redesigned from 1929. High up on the frontage are statues of St George and Britannia sculpted by Charles Sargeant Jagger. It was owned by Thames House Estates until it was sold to the British Government in 1994. Thames House Estates was jointly owned by ICI and Prudential for many years and subsequently was wholly owned by ICI. The building has been listed Grade II on the National Heritage List for England since 16 January 1981. MI5 and NIO headquarters Thames House was first used by MI5 between 1934 and 1939: the service was located on the top floor of the South Block. The service relocated to Blenheim Palace for much of the Second World War and then moved to Leconfield House after the war before relocating to 140 Gower Street in 1976. The dispersed and dilapidated state of its previous buildings at 140 Gower Street (headquarters) and Curzon Street House (registry, administration and technical services) led MI5 to seek a new home in the late 1980s. The Secret Intelligence Service (MI6) were engaged in a simultaneous hunt for new headquarters and consideration was given to co-location of the two. However this proposal was abandoned, due to the lack of buildings of adequate size (existing or proposed) and the security considerations of becoming a