Why didn't my MoT pick up why my brake was binding?

I had a an MoT carried out on my motor caravan this year. It failed on a rear binding brake and I was told to take the wheel off and tap the brake drum to free the brakes from binding. I did this and then took the vehicle back, only to be told the brake cylinder was seized solid and the brake did not work at all. I'd like to know why this wasn't picked up on the first test?
All the MoT could pick up was that the brake was binding. Not why it was binding.
Answered by Honest John on

Ask Honest John