Don't look down! Yeah, whatever you do, don't look down! The others are on the beach, lobbing up calls of encouragement, trying to make it easy for me, like it was for them. They clambered happily down the ladder and jumped on to the beach without noticing me, frozen at the back of the group like a horse refusing to jump a fence.
Now their voices echo round my spinning head. I lock my fist around the rusty handrail, close my eyes and listen to the rasp of the surf on the shingle below, try to synchronise it with the waves of nausea in my stomach, try to find a rhythm, something steady for my body to cling to, something slower than my thumping heart. I take a deep breath and look down. The ground zooms in and lurches giddily away again.
I snap my eyes shut and everything is still. I have heard people talk about this feeling, about how they feared the fall or fought the impulse to jump.
As a boy, I climbed to the top of a castle keep with my father, then had to help him down when he saw how high we were and his legs turned to jelly. I remember laughing at the story in a newspaper of a window cleaner so afraid of ladders he only worked on bungalows. I had been half amused, uncomprehending, never having known what they meant. Until now.
People call it vertigo. But I remember - from a pub quiz question, I think - that the proper word for fear of heights is acrophobia. Vertigo is an imbalance caused by damage to the inner ear. A medical condition, not a phobia.
Come on, let's go! A shout breaks my daydream. They are getting impatient, they wat to get on, there's a cafe and a cup of tea waiting another mile along the beach. Get a grip. Rationalise it. How far can it be? Twenty, maybe 30 feet? Two flights of stairs, that's all. What's the worst that can happen? A broken leg. Someone would call the air ambulance on their mobile. Never been in a helicopter before. Might make the local paper. My pulse has slowed. Maybe I can do this.
I turn around and step backwards on to the first rung down. Three points of contact at all times, that's what they taught us when we went climbing. I'm coaching myself under my breath - keep going, keep going - blocking out everything except the task in hand. My arms are tight, straining at the handrail, hanging on then letting go, moving quickly and grabbing hold, first one then the other. My legs are shaking, stamping on the steps, jarring my instep even though I'm wearing thick-soled boots.
And then my foot crunches on stones and I'm down. The voices of my friends and the sound of the sea and the smell of the spray and the sunlight on my face and a feeling of relief all rush into my head.
Someone puts an arm around my shoulder and makes a joke. I laugh and look up at the ladder, cursing the person who put it there. Slowly, unsteadily, I walk down the beach, trying not to show how scared I had been and wondering where fear comes from.
Vertigo explained by TV doctor Mark Porter: www.guide-information.org.ukdr_vertigo.htm Surgical treatments for vertigo: www.cscd.nwu.edupublic balancesurgical.html
Hitchcock's film: http:us.imdb.com Title?0052357