Last year, on my 55th birthday, I received an email from a woman called Connie Diletti with an enticing offer. Diletti was the producer of an annual conference in Toronto called IdeaCity, a gathering of 50 speakers talking about big issues such as climate change, food science, and the possibility of Canada merging with the United States, and she wanted me to be a part of it.

This year there was going to be a section about love and sex, and she asked whether I would talk about love letters (I had written a book about letter-writing, and my best examples were all about love in one way or another). I had never been to IdeaCity or Toronto before, and I had always wanted to see Niagara Falls nearby, and so I expressed genuine interest in attending.

I emailed back, asking what the deal was: how many hotel nights would IdeaCity pay for? What was the story with the flights? Connie Diletti's reply had all the sweeteners. In exchange for a 17-minute talk I was offered airfare, a five-star hotel, an HD video of my talk hosted on the IdeaCity site for ever, organised parties every night, and "a special speakers' brunch on Saturday at Moses's home".

There was more, but these were the salient points. The most salient of all was the fact that I was only required to speak for 17 minutes. Not my usual 45 with questions, and not the more rounded 15 minutes or even 20 minutes. Why 17, I wondered. Was this magical number arrived at after years of careful analysis? (IdeaCity was in its 16th year, a mere upstart compared to the 25 years of TED conferences, with which it bears comparison, but certainly old enough to have garnered a clear idea of when the audience tended to fall asleep.)

Or was the 17-minute slot mine alone, with other speakers given what may simply have been equally random durations? Would Lord Lawson, another participant, be given only 12 minutes with which to deny global warming, his current specialty? Would Dr Amy Lehman be granted 28 minutes to talk about the abuse of malaria nets by the banks of Lake Tanganyika? Would the best speakers with the sharpest patter and the funniest slides – there was a university man due to talk about the science of icebergs – make their sessions just fly by, while others, speaking for the same time on "the myths of garlic" or the "rap guide to religion" seem interminable? And who was Moses?

The sweet spot

When I arrived in Toronto three months later it turned out everyone else had precisely 17 minutes too. I learnt that TED talks were all intended to be precisely 18 minutes, a period that Chris Anderson, one of its curators, defined as the sweet spot: it gave the speaker enough time to be serious, but not enough to be academic; the "clarifying effect" of concentrating a message into just 18 minutes worked equally for both the speaker and the audience, with neither party having enough time to get bored; and it was the ideal time for a talk to go viral online because it was about the length of a coffee break.

But at IdeaCity, the 17 minutes was, in the words of Moses, "a bit of a f*** you" to TED. Connie Diletti told me that IdeaCity began in 2000 under the name TEDCity, in partnership with TED co-creator Richard Wurman​ (TED began in 1984). For a while, each speaker at TED and TEDCity had 20 minutes on stage, but when TED changed to 18 minutes and the organisation expanded and changed direction a little bit, Moses decided to go his own way by formulating the "f*** you" element. (Plausibly, sometime in the future, a rival organisation, inspired by IdeaCity but wanting to better it, would just reduce the time again, to 16 or 15 minutes. Or even eight. It was all about essence, reducing it down like a good French stock.)

Moses was Moses Znaimer​, a Jewish Lithuanian septuagenarian media tycoon, a local combination of Rupert Murdoch and Hugh Hefner, albeit more liberal. He was a charmer, but I sensed that he hadn't got to his elevated position by being a charmer all the time. The television and radio stations and baby boomer cultural/political magazine called Zoomer outlined in the email were all his, and he also liked to surround himself with beautiful women and beautiful cars (he ran a DeLorean and a classic Jag).

He also ran the show at IdeaCity, introducing each session and speaker, posing for photographs with each participant, and would act as the unofficial timekeeper. The official timekeeper was a prominent rectangular digital clock on the stage that began its countdown as soon as you opened your mouth. But the unofficial timekeeper was stealthier. As soon as you reached your 17-minute limit, Moses would appear on the side of the stage. If you exceeded it by a minute, Moses would slowly edge towards you, and if you went over beyond that, Moses would creep closer still, until he'd be standing beside you, ready to intercede with a witty and possibly deflating remark.

Fortunately I was on in the morning of the second day, leaving plenty of time to absorb the previous timekeeping of others and get unusually nervous. The event was held at Koerner Hall, a horseshoe-shaped venue seating more than 1000. It was the home of the Royal Conservatory of Music, and so the sightlines and acoustics were both magnificent, as was the screen technology for your PowerPoint​.

Of course, this only served to crank up the nerves, as did the fact that it was being filmed and, as the initial email promised, "hosted on our site forever". The world could meet its slow and terrible end, quite possibly caused by one of the terrible ecological or humanitarian catastrophes described in an IdeaCity lecture, but my talk would still be up there, somewhere, being enjoyed by no one.

Performance anxiety

When you're speaking for almost an hour you have time not only to meander and lose your thread, but to pull it all together again before the end. If you miss something out in the first half, you can thread it back in during the last quarter, or perhaps even during the Q and A afterwards. But 17 minutes is unforgiving; there can be no longueurs, no recaps, no sidesteps. Besides, the audience had each paid $5000 Canadian to be there, so you better be hot.

My morning arrived. The lavish ring-bound programme stated I was due on at 10.01. Initially I assumed this was a misprint, but then I saw that other speakers began at equally precise and stupid times: 11.06, 1.57, 3.48. In the hour or so before I was due on I learnt that many speakers rehearsed their speeches down to the last twitch; they trimmed and trimmed until it came in at 16 minutes 30 seconds, allowing time for mid-talk laughter, gasping and breathing.

I used to have a great fear of public speaking, something I traced back to my debilitating stammer at school. Words would simply take ages to come out, and some words, such as those beginning with "st", I just couldn't say at all. The school environment is not a good place to work on such a handicap. Addressing the class was one dread, but it was nothing compared to addressing the whole school at assembly, something we were sporadically required to do.

My other problem was that I liked to show off, and my stammer meant that I was doubly frustrated. My apprehensions continued when I was asked to publicise my first books, but gradually the anxiety eased, and my speech improved, and I began to look forward to book festivals. I liked the idea that I had conquered my fear. But now, watching others deliver perfect 17-minute sequences in smooth succession, my doubts returned.

Fortunately, the woman who was on at 9.31 a.m. – a talk about a new form of dating in which she would offer valuable presents to her friends if they set her up in a relationship that lasted (if it lasted until marriage she would reward the friend responsible for the set-up with a vacation worth $2000) – mistimed her talk dramatically. She ran out of material after 11 minutes, and the rest of her session was spent answering tricky questions from Moses, such as "it does sound a little cold-blooded, don't you think?"

The man who was on after her and just before me, at 9.41, was a pro, and had a carefully ordered pile of cards and a funny set of slides. His topic was a gift to any audience members weary from the heavier issues of the day before, which had included "Therapeutics for Age-Related Disease" and "The Vegan Advantage"; now we were going to hear how the emergence of self-driving cars would be a boon to vehicular sex. He went down extremely well (ha ha).

Exercise in compression

Only now did I wish that I had rehearsed and timed things. I thought I began okay, if a bit washily. Before I came on, the producers had shown a brief clip of Benedict Cumberbatch​ reading a love letter from my book, and so I began by apologising that Benedict wasn't here to read it in person, which got a generous snigger.

I then talked about how letters had told our history for 2,000 years and that tweets would make a poor substitute, not least to historians, and by the time I first glanced at the countdown clock I had already used up eight minutes. I had seventeen slides to show, and at this point had only clicked through two. I didn't quite panic, but I was aware that my brain was telling me several things at once, none of which I could share audibly: I was running out of time; they had paid for me to come all this way, and I wouldn't be worth it; Moses would encroach; I was about to be found out; why, with all this fancy technology, did the person in the control room not put my PowerPoint in "Presenter View" so I could see which slide was coming up next?

These were clear thoughts, and may have taken far less than a second to process, but I remember looking at the audience blankly for at least five seconds. (Neurophysiologists suggest we may be able to process information from visual stimuli in just 13 milliseconds; non-visuals connect faster still.)

The rest of the talk became an exercise in compression and how to maintain a sense of coherence in a limiting timeframe. As such, it was like life itself. Time had become my enemy. On the practical side I had hoped to inform and entertain and do a little pleading on behalf of the value of letters (terrible irony: letter-writing had ultimately been defeated by time and the speed of the alternatives), and suddenly I had nine minutes in which to flick through 13 slides and tell stories that usually took at least half an hour.

There is a limit to how well one can shorten a story before it crumbles to nonsense. I had now entered into a dimension I couldn't remember being in before: a sad and immediate private battle against a clock. But the clock was only visible to me, and the audience was oblivious, although perhaps aware that I was talking faster and looking slightly frantic.

Taking my time

With three minutes to go I had eight slides left. I didn't have to show them all, or tell all my stories as intended, but I had a possibly funny line at the end that I was wholly reluctant to jettison. I scurried on. Air seemed to vanish from the hall. I now couldn't keep my eyes off the clock, and its pace was alarming. Moses made an appearance stage left and hovered. I zapped through the slides like a panicky boy listing over-learnt facts in a history exam.

Then my time expired and the clock turned from green to red and started flashing. I said something like, "I've got two or three very quick things to leave you with". I glanced to my left: Moses trod water and politely stayed where he was.

I went about seven minutes over. I thought I'd botched the whole thing, but afterwards people were complimentary. Although this had been an extreme case, and self-imposed, the experience made me realise how destructive an over-concentration on time could be. Designed in this instance to provide a framework, a focus of concentration, it only succeeded in restricting those areas of my brain engaged in free thought and imagination. It was as if I was falling from my bike, my brain automatically closing off all the pathways except those essential to not talking nonsense as fast as I could.

At the other extreme, could something be said for talking nonsense very slowly? What would happen if, as in the example that follows, the clock never flashed, and time looked as though it would never run out? What if one could go on speaking for ever?

This is an extract from Timekeepers – How the World Became Obsessed with Time by Simon Garfield, published by Canongate, $32.99