I was preparing for O Levels at the time (a strange prehistoric version of GCSEs, for those who don't remember) and I remember finding myself in instinctive sympathy with the underdog - the Liberals had won six million votes but only 14 seats. It was a travesty.
Looking back, it was the first time I identified with the Liberal Party, though I didn't actually join for another five years.
It all seems rather a long time ago, over the horizon of history. So it has been strange reading about the events on the BBC website, and hearing - by sad coincidence - of the death of Marion Thorpe in the last few days.
I was a great admirer of Thorpe's in those days, and have since been lucky enough to meet him and Marion at their home a number of times.
I still think he was, and is, an extraordinary man, despite the events that followed. But looking back, I wonder if his leadership did not fall into the classic Liberal trap: high intelligence, a compelling presence, but another Liberal ecstacy of positioning rather than anything important to say.
It has been the besetting sin of the party I joined for most of the past century.
I joined in 1979, for two reasons. One was that I interviewed the Liberal candidate for Oxford for two whole hours at the height of the election campaign, as a student journalist. By the end of the conversation, I was completely convinced.
But there was another reason. The stance of the Liberal MPs the previous year, going into the no lobby alone against the reprocessing plant at Windscale, as we called Sellafield on those days.
At least half the reason I joined the party was that it realised, when none of the other Westminster parties did, that nuclear energy would be vastly wasteful and centralising.
Looking back, I couldn't have joined any other party. I am a Liberal, despite the recent app which allows you to rate your political position, which concluded - despite all evidence to the contrary - that I was a Scottish nationalist (this was not useful advice: it is some years since the SNP fielded candidates in Croydon).
But I've been mulling over my four decades rooting for the Liberals and Lib Dems, since the aftermath of the February 1974 election - almost my entire adult life. Like most of my friends in the party, we all spend at least as much time frustrated with the party as we do campaigning for it, but usually - being Liberals - for different reasons.
Looking back, I think I came to the conclusion some years ago that - if I was to play any useful role in the party - it would be to try and tackle this besetting sin: the preference for positioning over thought.
Which brings me back to the nuclear issue. I support the coalition, but no issue has made me more enraged with my own party's besetting sins than the vote in September to back nuclear energy, but without a state subsidy.
Nothing preys on my mind more than that. The embarrassing self-delusion involved. The stupid, thoughtless positioning.
As if an industry that produces high level waste without any storage facilities, except its current temporary one on the surface at Sellafield - and without any prospect of storage facilities (three Albert Halls of it so far) - which will stay dangerous for 100,000 years.... As if we can pretend that will involve no subsidy.
So for the sake of Lib Dem positioning, we hand the next 2,000 generations the task of protecting and paying for this stuff - for millennia after the disappearance of any of the companies we are subsidising.
I find it quite staggering that we could have made a decision so transparently delusory, just to help our Secretary of State get over a little political difficulty.
Yet, here I am, four decades after my O Levels, toddling off to the party's conference York. A strange thought.
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