I'd be wary of ignoring it if it's anything to do with the council.
If it's from some Portakabin based knuckledragger firm just totally ignore it. Don't plead innocence, just ignore.
If it's the council, they usually have photographic evidence that your ticket wasn't displayed. The one in Brum did when I tried to get away with it. Ticket had honestly blown off the dash when I shut the door. I showed them a valid ticket, but they just kept pointing to failure to display a valid ticket.
What annoys me is that, if I hadn't bothered buying a ticket I'd be no worse off.
Face it, your just an honest law abiding citizen against a morally corrupt regime.
Those in positions of power won't change the system as they can just get tickets cancelled at will anyway.