I have only vague memories of walking holidays in N Wales back in the 70s, but Tryfan does ring a bell. IIRC we followed the path up until it got too rocky. My mum stopped with the dog to guard the sandwiches and my dad and I pressed on for a bit before saying sod this, and returning a for sandwich. One or the other of my sisters may or may not have been present. I'll add that it was pouring with rain. I don't actually remember that but it always was on our N Wales holidays.