Each year, as the American Thanksgiving holiday draws near - it takes place on the fourth Thursday in November, which this year is the 23rd - two sets of images, from consecutive Thanksgiving seasons, come back to me.
In both cases they link an American military outpost in Co Derry with events in the United States and beyond, and in both cases they recall an international climate of anxiety and shock.
In the autumn of 1962 I was a television reporter with BBC Northern Ireland, based in Belfast. As the newest kid on the block I was rarely assigned the big immediate stories. What came my way were background features, show business interviews, vox pops, that kind of thing. So it was to me that the news editor turned one day with his hands across the ocean idea. He wanted to mark Thanksgiving with a film report from the Nato communications base at Clooney on Lough Foyle, a report which would sketch out its history since American forces arrived during the second World War and include interviews with current US navy personnel. In principle the navy accepted this proposal but I was asked to visit the base for a preparatory meeting to discuss details.
The meeting was set for Tuesday, October 23rd.
On the eve of that meeting, however, President John F Kennedy made a television broadcast which changed everything.
He announced that the United States had unmistakable evidence that the Soviet Union was installing nuclear missiles in Cuba and that he had ordered a naval blockade of all military equipment under shipment to the island.
He warned that any missile launched from Cuba against any nation in the western hemisphere would be regarded as an attack by the Soviet Union on the United States, "requiring a full retaliatory response on the Soviet Union".
In reply Soviet leader Nikita Khrushchev protested that the weapons were defensive and that the blockade " may lead to catastrophic consequences for world peace".
My news editor told me not to telephone the Clooney base but simply to show up.
"If you speak to them now they're bound to say don't come."
I was to go alone, as previously agreed, but if an interview proved possible a film crew could be fetched from Derry in 15 minutes.
"I can't believe you'll get an interview, but it could be your first scoop, and possibly your last."
As I drove towards Derry I could gather from the car radio that the story was getting grimmer by the hour. Soviet supply ships were still heading for Cuba. What would happen when they met the American blockade?
Nevertheless, when I identified myself at the security post on Limavady Road I was directed without fuss to the office of the base commander. He apologised that the current state of high alert meant he could not show me around.
I asked, as he knew I would, for a news interview and he told me, as I knew he would, that he couldn't give one.
What he did want to do, though, over coffee and doughnuts, was talk.
Everyone stationed at Clooney, he said, had been made so welcome by the local community that they would be delighted for the film project to go ahead if and when the crisis passed.
He showed me a framed photograph of his wife and children who were visiting relatives in the States and with whom he had hoped, until now, to be reunited for Thanksgiving. Clooney was a major communications link between Washington and American naval forces in European waters, from the Atlantic to the Mediterranean. If nuclear hostilities were to break out, therefore, the base would be a likely Soviet target. Should that happen, I reflected, as I drove away, the siege of Derry would no longer be the most vividly remembered event in local history, assuming there would be anyone left to remember anything at all.
The following day the Soviet ships turned back and the immediate risk of conflict had passed. But the crisis was to continue for several weeks before the missiles in Cuba were dismantled and shipped back to the Soviet Union.
By the time Kennedy ended the blockade and the alert was relaxed it was too late to revive BBC Northern Ireland's Clooney project.
Both sides were happy, however, to make an advance date for Thanksgiving 1963.
There were only six days to go when John F Kennedy was shot in Dallas. Once again my regional feature story had been overtaken by the world's biggest news event.
This time, though, the base commander requested that we should come, obviously not for the original purpose, but to film a Thanksgiving tribute by American servicemen and women to their murdered president. I remember the candlelit photograph, the book of condolence, the communal sense of shock and loss.
And I remember a woman naval officer talking to me about the first Thanksgiving in 1621 when America's colonists had not only given thanks for their first harvest but had prayed for those who had not lived to see it. And she told me of a Thanksgiving poem:
"Count your blessings instead of your crosses.
Count your gains instead of your losses."