For a third day, thousands of Heathrow passengers are suffering delays and cancellations due to poor visibility.

“Arrivals regulated due to weather (freezing fog),” reports Eurocontrol. “High delays peaking around 1100.”

British Airways has cancelled 20 flights to and from Heathrow, mostly serving domestic and German destinations. The airline said: “For safety reasons, Air Traffic Control has to allow greater space between landing aircraft in fog and this will mean a reduced number of aircraft being allowed to land each hour at Heathrow.

“As a result we are slightly reducing our Heathrow flight schedule, and other flights may face some delays.

We are sorry for the difficulties caused by the poor weather and will do all we can to minimise the effect it has on our operations.”

Lufthansa cancelled one round-trip to Heathrow from Frankfurt.

More than 250 flights have been cancelled since Monday, affecting an estimated 30,000 passengers.

Rail commuters in south-east London and Kent faced a second day of serious disruption following yesterday’s derailment of a freight train at Lewisham, one of the key junctions on the Southeastern network.