I was in Cornwall a fortnight ago and went sea fishing for the first time, had a good day caught these mackeral, and the kids had the pollack. But the rocks were covered with limpets, I got a few as you can see on the pic.
I used the blunt end of my priest to knock em off, I held it about 1/2 an inch away and smacked the other end. If you tap one then abandon it, all you do is end up smashing the shell.
I boiled em till they came away from the shell then sauted them in butter and, after trying them, felt I should have left them be. It was like chewing a rubber ( of the eraser kind!! ).