In a bit of a hissy fight among British airports, London City Airport is the winner with the right to advertise that it's the only airport "actually in London," as it claimed in a commercial last summer.
Competitors, including Heathrow, challenged the claim as misleading, but the Advertising Standards Agency has ruled in London City's favor, noting that it's the only one of he capital airports with a London postal address.
The other airports, including Heathrow (in Twickenham), Gatwick (West Sussex), Stansted (Essex) and Luton (Bedfordshire) can still use London in their names. And Heathrow continues to point out that, with Underground connections and two dedicated rail services, it's the best-connected.
Two other airports, London Southend and London Oxford (Kidlington) also use the capital name, although they are long distances away.