A couple of weeks ago, I planned to meet my wife in Crawley town centre (as she had gone out somewhere first) and as it was a Sunday, we parked on the High Street as we always do. We went to a restaurant there and when returning were shocked to find that both cars and all other cars next to us had parking tickets!
It turns out that you cannot park where we parked and that had always been the case, but we had been doing it for years as thought it was somewhere you could park for free on Sunday (as if there is such a thing any more).
When I got home I sent them an email challenging the tickets asking them to be lenient as it was both of us and we had to rush in to the restaurant as our 1-year old son was hungry. Unfortunately they did not and we had to pay anyway - luckily only £35 each as was within 14 days.
The moral is to always look where you park and never assume anywhere is free unless the signs specifically say so. Also, don't expect councils/parking companies to be compassionate about your circumstances as unless you had to stop due to having a heart attack, then they won't let it go.