For transfers directly between London's airports, the fastest way (short of a taxi) is the direct inter-airport bus service by National Express. Buses between Heathrow, Gatwick, Stansted and Luton run at least hourly, with Heathrow-Gatwick services taking 65 min (£18) and Heathrow-Stansted services 90 min (£20.50) (note that services between Stansted and Luton run only every two hours). However, it's essential to allow leeway, as London's expressways, especially the orbital M25 and the M1 motorway, are often congested to the point of gridlock. Some buses have toilets on board.
There are several ways to get to and from London City Airport.
Rail: Getting there and away is easy by public transit with the Docklands Light Railway (DLR) operating for connections to the City and Canary Wharf.
Bus: London Buses services 473 and 474 run to local East London destinations.
Car: There are short-term and long-termin parking places and car rental facilities at the airport, and taxis are available outside the terminal.