I WAS about 25 at the time this was taken, and a teacher - a very serious teacher.

The background is that I had put forward a motion at the conference of the Educational Institute for Scotland proposing that they should support the use of a ship for educational cruising during term-time. I had also written a book, called The Case for Ship Schools, which was seen by a young student friend of mine called Brian Redhead, on the then Manchester Guardian.

Brian wrote a friendly leader saying at least it is worth trying to give this man Tam Dalyell his head, he might have a good idea, and it was seen by British India, a subsidiary of P & O, at the very moment that they had a problem. They had a 12,000-ton troopship, the Dunera, coming off government charter and were looking for a use. So they got in touch with me, and the long and the short of it was that I was appointed deputy director of studies.

This was 1960 and we took parties of pupils to Spain, Gibraltar, Portugal, Greece - where this photo was taken - Oslo, Copenhagen, Hamburg . . .

I spent two years on the Dunera, 13 days on and about three days off and then the turn-around. I worked an 18- hour day. I was a toughie, generally, because I was the teacher responsible for discipline: the number of people who, 30 years later, still come up to me with a smile and say: 'You were the bastard who hauled me out of my bunk to write out the ship's fire regulations . . .' which I always did with any dormitory that caused trouble.

Well, actually, I'm forgiven because for many it was a formative experience and thousands say: 'I was on the Dunera and it was wonderful.'

It was wonderful. It was very hard but I was extremely fit and I was good at it, frankly. But I'll tell you exactly what made me come away. I was in the Mediterranean and I got a telegram from my mother saying: 'You have been nominated for the West Lothian constituency.' (Boundary changes later created Linlithgow from this constituency.) There was a by-election and what had happened was this: I had taken abroad boys' football teams in the past and one of these boys was a difficult, awkward youth who got on well with me.

His grandfather was the local boss of Nacods - the National Association of Colliery Overmen, Deputies and Shotfirers - who decided I had to be rewarded and so he gave me the Nacods nomination that was within his grasp. With that, I became a serious candidate and to my astonishment I was selected: that was 1962, in the famous by- election when the Tories lost their deposit. It was chance. I once told this story to Ian Mikardo and he said: 'Well, I've known worse reasons for being selected.'

Eventually, more than a million pupils went on those cruises. The Dunera was succeeded by the Devonia then by the Nevasa and eventually by the Uganda, which was taken over as a hospital ship during the Falklands War. That brought it to an end because the Uganda was so battered in the South Atlantic.

It was one of the many reasons I think the Falklands War was a tragedy. I was opposed to the whole thing for quite separate considerations, but it brought to an end 22 years of constructive activity from which so many young people benefited.

Where my time on board made a tremendous difference was during the controversy over the Belgrano. I was the guy who was absolutely at home with co-ordinates, directions, fathoms and all the rest of it, and I knew from my knowledge of the sea that I wasn't being told the truth . . .

(Photograph omitted)