Anyone know how the steering lock works?

[Enoch]

Hi folks, my donor had a broken steering lock where someone had tried to pinch the car at some time. I bought a new alloy lock assembly ( the bit that the ignition lock goes in to) but the lock still does not work. I can turn the key and it all feels ok. Does anyone know if the locking mechanism is contained within the alloy part? I can't see any sort of latch sticking out so I don't know where to go with it.
Any words of wisdom would be much appreciated, as always.
Enoch.

[Enoch]

Thanks Adrian, I see what is happening now. Where the lock barrel goes in to the housing there is a sprung detent ball. As the key is withdrawn the pressure of the detent ball against a tang on the lock causes the rotating part of the inner lock to be pulled out. That causes the metal locking piece to engage with the steering wheel. My lock barrel is knackered so it does not pull the plate outwards as the key is withdrawn. So it looks like a new barrel will fix it.
Thanks for your response, it helped me look in the right place.
Enoch.