Thick fog which has blanketed large areas of southern England has resulted in the cancellation of more than 100 flights. The Met Office has issued a severe weather warning along the south and southern eastern parts of the UK as a result of the poor visibility.
The fog is expected to lift later in the morning (Monday 23 January), but it has already affected thousands of passengers. Heathrow, the UK's largest airport, has cancelled around 100 flights as a result of the weather conditions and is urging passengers to check their flights for updates on their journeys.
A statement from Heathrow said: "Foggy weather across London is expected on Monday 23 January and some passengers may experience disruption to their journey as a result. Heathrow advises passengers to check their flight status with their airline before coming to the airport.
"Heathrow's top priority is the safety of passengers and we apologise to those whose travel has been affected."
There have also been cancellations at London City Airport, with Gatwick also cancelling one flight. All London airports are warning passengers that flights are experiencing cancellations or delays and to check with the relevant airline for further information.
A Met Office spokesperson said: "Areas of fog are likely to start to form in places during Sunday evening but the main problems would appear to be more likely later tonight and through the Monday morning rush hour. By this stage, the western part of the warning area may be seeing improving visibilities.
"Areas of dense and freezing fog may lead to journeys taking longer than usual, with possible delays to air travel. Watch out, too, for slippery surfaces.
"As the cold air mass across much of the south of England moistens up, there will be a much greater risk of fog than on recent nights. Areas of cloud trying to advance from the west will add to the uncertainty in extent of fog later in the night and through Monday morning."