Thick fog forced the cancellation of ten flights from Heathrow and London City airports by 6.30am on Monday, as forecasters warned that visibility could fall to 50 metres or less.

Seven flights from Heathrow and three from London City had been cancelled. A yellow fog warning covers London and most of the South East until 11am, with the Met Office warning of difficult conditions for morning travel.

The fog was expected to persist well into the morning. Meteorologists attributed its formation to light winds, clear skies and the longer autumn nights, which give temperatures more time to fall. Colder air is already closer to the temperature at which it becomes saturated and fog forms. Below-freezing temperatures can make the fog particularly slow to clear the following day.

The disruption extends beyond air travel. Motorists have been urged to take extra care and allow more time after a recent crash involving more than 30 vehicles during foggy conditions left a motorway closed for nearly 12 hours.

AA president Edmund King previously warned that familiar roads can change within minutes as fog develops. He urged drivers to reduce their speed and leave a larger gap to the vehicle ahead, rather than relying on its rear lights as a guide.

Following those lights can create false reassurance while leaving too little room to react if the vehicle suddenly stops, he said.

“Ultimately, there’s no prize for arriving a few minutes early. Give yourself extra time, slow down and drive to what you can actually see ahead.”