I think my moment of terror was from a local seaside park at Pleasure Beach Gt Yarmouth.
When I was about 10 I rode a portable top spin ride called Terminator. Everything was ok as I sat in my seat, but things took a turn for the worse when the restraints came down. As Im sure most of you are aware, top spins have an over the shoulder harness and a secondary lap bar which clamps against the outside of the OTSR. All of them worked, apart from mine, where my lap bar came down first before the OTSR. This left one hell of a gap around my body to the point where I could easily slip out of the ride. Despite my shouting and shear panic the ride started.
Lets just say I was flung all about in my seat and I came off with large bruises and red marks all over my back. Because I knew something was wrong I clung on for dear life, had I been unaware, it could have been worse. After speaking to the ride operator he said nothing came up as wrong on the system and he kind of shrugged off the problem. Think he thought otherwise when I showed him the marks on my back!
I have, however, overcome my fear of top spins about 4 years ago (about 8 years after the incident) and now I think they're great. However I'm still not the biggest fan of portable rides!