above them , on the flat roof , were the three squat masts of one of the most powerful transmitters in england , explained on the bold bronze list of occupants in the entrance hall of the building by the words 'radio tests ltd. ' the other tenants were declared to be 'universal export co. ' , 'delaney bros. ( 1940 ) ltd. ' , 'the omnium corporation ' , and 'enquiries ( miss e. twining , obe ) ' .