It’s one of the more irritating events in life – when you lock yourself out of your phone and have to produce your PUK code. Cue the search for the box that the phone came in, which is never where you remember putting it.

So what is this elusive PUK code and why do we need it?

Unravelling the mystery starts with spelling out the acronym. PUK stands for PIN unlock key. And that’s exactly what it is. The PUK is a number uniquely associated with your SIM card. It’s usually eight digits long and is the sole identifier of your unique SIM card. It’s used to prevent unauthorised use of your account and keep the details on your SIM safe - so for this we should be grateful.

You’re usually asked for the PUK code if you’ve entered the PIN three times incorrectly. This suggests to the phone that you might not be the person who owns the SIM so it’s literally putting up a defence system. Once you’ve been asked for the PUK code, the phone cannot be unlocked without it – despite your best efforts at resetting it, talking nicely or throwing it against the wall.

For more information on how to retrieve your PUK code if you don’t have the box handy, read here…