A foggy Christmas is forecast as Heathrow flights are grounded

Thick fog caused chaos at Heathrow yesterday and thousands of passengers were warned not to travel to the airport as airlines were forced to cancel at least 160 flights.

The worst-affected airlines were British Airways, Lufthansa and Alitalia. BA predicted further severe delays today, with the thickest fog expected to linger for 48 hours. There were also delays at Gatwick airport, but only two cancellations.

More than 150 passengers on an Irish Ferries boat sailing to Pembroke in west Wales were delayed for ten hours overnight after fog forced the closure of the port. The boat docked at 11.30am.

The Met Office said the mist and fog would continue in southern areas until the weekend. Temperatures are expected to be between 1C and 4C.

A BA spokesman said: "We will have to see how the weather develops but there are likely to be severe delays and possibly cancellations to many short haul and domestic services to and from Heathrow."

Motorists are also likely to face disruption despite the suspension of all major roadworks between 22 December and 2 January.