One mid-August morning we were cycling to a favourite picnic spot at Bar Point, a deserted part of the island. There was a small beach there where we planned to have lunch, and a little bay where a few moored boats bobbed in the rising tide. I was with my parents, my 16-year-old brother Simon, his friend Robert, and my younger brother Matthew, who was 10. It was Matthew who spotted an empty rubber dinghy bobbing out to sea. Simon and Robert ran to the beach to see if they could catch it.
I waited with my parents on the clifftop. Suddenly, my father cupped his hand to his ear - he said he had heard a faint cry for help. We too recognised the unmistakable sound of a human voice in distress. My father hurried down to the beach. "What is your trouble?" I heard him shout. "I can't get into my boat," came the faint reply.
My father sent Robert off to alert the coastguard while he and Simon found a small wooden dinghy and carried it to the water's edge. My father rowed out and Matthew and I watched from the shore. Chained to a hut on the beach was an affable and unperturbed-looking golden labrador, whose ears I absent-mindedly stroked.
About 400 yards out my father and Simon pulled alongside a small launch. Submerged in the water and clinging to the fender rope was a grey-haired man. While my father steadied the boat against the strong tide, Simon clambered on to the launch, grabbed the drenched figure by an arm and a leg and hauled him on deck like a sack of potatoes. Then he waited for him to catch his breath, before Dad rowed them all back to the beach.
"Look," I said to Matthew as the boat drew near. "It's Harold Wilson!" Mr Wilson staggered ashore, his face white with cold and shock, his teeth chattering. I wondered whether his gold watch was waterproof. He told us he had slipped out of his rubber dinghy as he attempted to get into the launch, and had been unable to pull himself out of the water. He had been in the sea more than half an hour.
He declined my father's offer to take him back to his bungalow, saying that he didn't want to be any more trouble. My father replied that it was not every day one pulled a former prime minister out of the sea. Then Mr Wilson untied his dog, Paddy, and we parted company. Dad swore us all to secrecy - if the story got out it could ruin our holiday, and Mr Wilson's.
Next day, quite by chance, we bumped into him. I thought he would be pleased to see us, but he just looked embarrassed, even anxious to avoid us. In answer to my father's polite enquiry, he said he was much better, although his arm was still stiff. We didn't hear from him again.
We kept quiet but, somehow, a month later the story slipped out. It was national, front-page news! "Wilson Rescued in Sea Drama", "Wilson Snatched From Drowning", "Scilly Secret Floats to the Surface", the headlines read. Most of them made us laugh, but the Daily Mirror's we thought outrageous: "My Dog Tipped Me In" it said. Mr Wilson's press secretary, Joe Haines, had blamed Paddy. There was even a photo of the dog captioned "The Culprit"! One could see the need for damage-limitation - after all, it was embarrassing for Wilson, not least because Edward Heath was a serious yachtsman - but Paddy, I know for sure, was innocent.
My father was besieged by television crews outside his office and questioned about his voting habits. "Lifelong Tory saves Wilson from Drowning" ran the Telegraph's angle on the story next day. Other papers pointed out that the Labour leader, whose party was pledged to end private education, had been saved by a public schoolboy. And so it went on. We put up with myriad jokes of the "Why didn't you throw him back?" variety. Joe Haines made light of the incident. Wilson, he claimed, was in "no danger", he "could have swum to the beach" but was "waiting for a friend to turn up". While doing a spot of deep-sea paddling no doubt.
Harold Wilson would almost certainlyhave died. He was 57, he was overweight, he'd been in the freezing water for more than half an hour and his arms were giving out. The Atlantic currents were very strong, there was no one around, and it was only by the slimmest chance that my father heard his cries. He knew he he had had an extremely close shave, but had obviously been persuaded to let the dog take the blame and play down the incident.
And if he had been found belly-up in the Bristol Channel? The course of British politics might have been somewhat different. Callaghan, Healey or Benn would have succeeded him, Edward Heath might not have been defeated in 1974, there would have been no Tory leadership challenge in 1975, and quite possibly no Thatcher leadership. My brother Simon, now a toxicologist, sometimes speculates (miserably) that our father may have inadvertently launched Mrs Thatcher's prime ministerial career that fateful August day. The rest, as they say, is history.