Thousands of air passengers face possible disruption at London's main airports due to foggy weather after temperatures dropped to as low as -4C last night.

A yellow warning of fog is in place until 10.30am, but freezing temperatures and low winds could see it persist into the afternoon, Met Office forecaster Mark Wilson said.

With all the capital's airports with only 100 metres of visibility this morning, Heathrow Airport is urging passengers to check their flight status before they leave home.

The Met Office has issued a yellow warning of fog for London and southern England that is likely to affect the morning rush hour.

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Areas of dense freezing fog could hit journeys and lead to possible delays to air travel until 10.30am, forecasters said.

A message on the Heathrow website 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.

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"Heathrow's top priority is the safety of passengers and we apologise to those whose travel has been affected."

Road users are also being warned of difficult driving conditions after freezing conditions overnight.

Temperatures will struggle to top 0C (32F) in the worst affected areas today, where fog is likely to persist.

Elsewhere highs of between 3C (37F) and 5C (41F) are expected.

A Stansted Airport spokeswoman said there had not been any cancellations, but advised passengers to check with their airlines for the latest information and allow enough time to get to the airport.