In article , Jethro wrote:

If it were a hydraulic failure, the idea is one will work if the other
fails. Of course if one has already failed...

Unless the wheel cylinder leaked and ****ed brake fluid all over the
shoes ....

Been there, done that, had the AA Relay van turn up without having to have
a patrol check it really wasn't a roadside repair first....
(It didn't just leak a bit past the seal - the casting had cracked.)