Verified answer

it really doesn't matter which of the 5 London airports you arrive at (Heathrow, Gatwick, Luton, Stansted, City) it's very easy to get to Kings Cross from all of them

once you've decided which airport to come to, post another question for directions

London City airport would be the nearest I should think - but it's not a big airport and I think only takes smallish planes, not long-haul. If you're coming from overseas you would probably want Gatwick or Heathrow - either would take you about an hour from Kings Cross.

Heathrow (Underground) or Luton (rail). Gatwick (rail - weekdays only; otherwise train to Victoria then Underground Victoria Line) have direct conections to St Pancras/Kings Cross. If you're in the U.K. Euston/St Pancras/Kings Cross railway stations are very close with direct rail services from Edinburgh,Glasfow,Newcastle,Manchester,Leeds,Sheffield etc www.nationalrail.co.uk