A Heathrow security worker was arrested in an airport toilet after seven kilograms of cocaine were seized by police.
The National Crime Agency said the man, a 30-year-old from Southalll, west London, was detained alongside a 37-year-old man from Colombia in the Terminal 5 bathroom on November 23.
Officers said the 37-year-old had recently disembarked a flight from Colombian capital Bogota.
A 43-year-old man was separately arrested in the arrivals area of the airport.
A fourth man, aged 46, was arrested following a search at an address in east London and all four are in custody and are being questioned on suspicion of drug importation offences.
Senior investigating officer Darren Barr said: "Heathrow Airport provided invaluable assistance in this operation, and working with partners such as the Metropolitan Police Service, Border Force and the Heathrow authorities we are determined to target those who may be involved in criminality at the airport."