The chairmen of FTSE 100 engineering giant Babcock International (LSE: BAB.L - news ) , British Land (LSE: BLND.L - news ) and the AA have put their names to an open letter from Heathrow chairman Sir Nigel Rudd urging ministers to support expansion of the west London airport.
In the context of the input sentence, determine the relationship between 'Babcock International' and 'London'.
Options: distribution format, brand, headquarters location, chairperson