What does the tyre pressure warning light mean?

The tyre pressure warning light comes on when the car's sensors detect that one or more tyres has noticeably lower pressure than it should. On most cars, it won't tell you exactly which tyre or by how much - you need to check all four yourself.

It's sometimes just normal pressure loss from cold weather rather than a puncture, but it's not something to ignore: driving on significantly under-inflated tyres increases the chance of a blowout, causes uneven wear, and is also a legal requirement to get right.

Check all four tyres with a gauge (petrol stations usually have a free or coin-operated one) rather than guessing. Never rely on a specific pressure figure from anywhere other than your own car's door pillar sticker, fuel flap or handbook - the correct pressure varies by model and how loaded the car is.

If a tyre keeps losing pressure after you've topped it up, that's a sign of a slow puncture worth getting looked at properly.