I had to get (yet another) one when I began helping the slow readers in our local Sec.school. I refused to do it and the School did it for me, with my attendance to answer questions.
I have an issue with this. In the 1990's I was a very active High Jump coach in the North. I was in demand all-over the place. Every club needed me to get a new clearance. I couldn't see the point of this as I was already cleared as a teacher with 2 Local Authorities and the Chief Constable (fed-up of the applications) wrote me an authorisation letter - to no avail, everyone had to stick by the rules. Eventually, I got fed-up and just stopped doing it - to the detriment of a lot of kids.
Back to OP - the 'employer' did it and I received the letter - which I have lost, 'cos I don't think I need to be certificated after my long history. If they want me, they can do it. I give them over 2 hours per week and they would have to pay me quite a lot if I went as a qualified teacher. The system annoys me considerably - surely 1 CRB check should suffice?