My mum noticed one of my car's rear tyres was looking a little flat. So I checked the pressure, and found it was dangerously low.

Normally it should be 26 PSI, but it was only 5.5 PSI. Oops. Very lucky she saw it, otherwise I could've ended up having an accident.

Update: I've actually got a slow puncture. I noticed the tyre was a bit deflated again yesterday, and I had to go to a petrol station to pump it back up again. Unfortunately by the time I got to one with a working pump it was almost completely flat, and I'm a little worried I might have damaged my alloy wheel since I was close to driving on the rim. That would not be good.