7.—(1) For an absence from the usual place of residence overnight in London or exceptionally in any other place in the British Isles approved by the Department, the rates may be increased by a supplementary allowance of such amount as the council may determine.
(2) For the purpose of this paragraph London means the City of London and the London Boroughs of Camden, Greenwich, Hackney, Hammersmith and Fulham, Islington, Kensington and Chelsea, Lambeth, Lewisham, Southwark, Tower Hamlets, Wandsworth and Westminster.