Car came with 2 keys and I only ever used one of them. When I did come to use it, it unlocks the doors ok but won't turn in the ignition barrel

Has this happened to anyone else? Anyone know any reasonable reason for this? Or should I just get a new key cut for it?

One day I'm bound to need the spare...

Go Compare (sorry) your keys. If you’ve only used one the previous owner may have just coded a second key and not had it cut. More likely though the wear on the barrel is not matched to the key so through lack of use. A million years ago they used to tell to rotate the usage of the keys. I’ve recently purchased a second key and got it cut. It was resistant so sprayed som WD40 on the barrel of the key and used it, worked a treat. 2006 2.7 TDV6 HSE in Cairns Blue.