Thick Fog blanket UK cities.

 Thick fog across much of Britain caused travel disruptions on Monday with 10 percent of flights cancelled from London Heathrow, Europe's busiest airport.

The Met Office said the fog could reduce visibility to less than 100 metres.

Heathrow said around 45 flights had been cancelled, while London City, Manchester, Leeds Bradford, Glasgow, Belfast and Cardiff airports all reported delays.

In foggy conditions, airports have to switch to radar and "low visibility procedures" to ensure aircraft can taxi, take-off and land safely.