The history of London is one of the specialist subjects of tonight's heat, which appropriately enough comes from the City University, in London. The contenders are:TIMOTHY BEAUMONT, freelance journalist on the Life and Works of Dorothy L. Sayers DENNIS BYERS, export clerk - Ancient Egypt from 2700 BC to 2339 BCCATHERINE SLATER, housewife - History of London from Roman timesSIMON FOSTER, teacher - Drama in Athens 500-388 BC