London issues a high air pollution alert as thick fog disrupts travel

If your commute looks murky this morning, that's not just your imagination. Dense fog has led to a "high" air pollution alert in London, and forecasters warn of difficult travel conditions and delays across much of the UK.

Mayor of London Sadiq Khan put the capital under the alert on Monday night. He urged those most vulnerable to be wary and to take precautions.

The fog is a big part of the problem. It can trap polluted air close to the ground. Reports also point to bonfires and fireworks from last week's Bonfire Night (5 November, when Britons set off fireworks) adding to the smog build-up.

Air quality maps turned red and purple over London, with boroughs including Westminster, Wandsworth and Tower Hamlets among those covered by the highest levels. Government monitoring showed many sites with fine particle (PM2.5) levels well above the World Health Organization limit.

The fog has also disrupted travel across England, Wales and Northern Ireland, with a further weather warning issued. If you're heading out, allow extra time and check your route before you leave.