According to Transport for London
King's Cross/St Pancras interchange zone is the UK's busiest transport interchange hub with over 95 million people passing through the interchange zone every year.
The overground stations are next to each other on the busy Euston Road, separated by Pancras Road.
The tube station has multiple entrances and is spread out below both railway stations.
The area as a whole tends to be referred to as King's Cross.
Journeys which require a change between the two stations, (or between one station and the tube) won't need more than about 10 minutes walking time but if you've not been here before it's a busy and confusing place and safer to allow 20 minutes or so. If you are checking in or arriving via Eurostar this will add to your journey time.
Euston Station is outside KXLDN's catchment area but is only a 5-10 minute walk up Euston Road or one stop on the tube.
How to get to London's airports from King's Cross St Pancras
Either: Tube via Circle or Hammersmith & City lines to Paddington then Heathrow Express
(faster, more expensive)
Or: Tube via Piccadilly line (slower but cheaper)
Either: Direct trains from St Pancras (these do not currently run at weekends or late in the evening)
Or: Victoria line tube to Victoria then Gatwick Express
Direct services from St Pancras to Luton Airport Parkway Station, from which there is a shuttle bus service to the airport.
Victoria line tube to Tottenham Hale then Stansted Express.