TV host Ortis Deley was dropped this week as Channel 4's main presenter of its world athletics coverage after an excruciating series of blunders. Jon Henley talks to other broadcasting veterans about the thrill, the adrenaline - and the nightmare of going live

It's tough, live TV. We tend to forget it these days, perhaps because there's so much of the stuff, but anyone in doubt need only ask Ortis Deley. Until this week the 38-year-old broadcaster, first talent-spotted as a contestant on Blind Date, had enjoyed a blameless career, mainly in children's and youth programmes on cable stations and at the BBC. For the past two years, he had co-presented Channel 5's The Gadget Show.

Now, following several hundred complaints and an excruciating three-minute YouTube compilation entitled Ortis Deley's Presenting Masterclass, he is probably better known as the man Channel 4 dropped as the main presenter of its first attempt at covering the World Athletics Championships.

Deley experienced what the BBC – which has covered the event for the past 27 years – described, with commendable restraint, as "some difficulty with the demands of live television". The Times critic Giles Smith was rather less considerate, writing that the presenter's performances in South Korea "brought to mind furry creatures and headlamps".

In the course of a few hapless days, Deley repeatedly stumbled over the names of star athletes ("the Honourable Leo Usain Bolt") and his trackside commentators. He called Oscar Pistorius, the South African double-amputee "the fastest man on no legs".

He invented events ("the men's 100-metre hurdles"), forgot commercial breaks, missed links, paused for long moments to consult his script, corrected himself endlessly, asked his studio guest – the four-times Olympic gold medal-winning sprinter, Michael Johnson – whether he was a pole vaulter, and concluded one broadcast with the memorable sign-off: "So we have a gloriously sunny day here in the studio. We've seen some action this morning as well. Jessica Ennis. Good night."

The perils of live telly, obviously, are many. No one, not even the most experienced broadcaster, is immune to the occasional slip of the tongue; the moment when the mouth releases the clutch before the brain has engaged first gear. Private Eye's Colemanballs, named after the great gaffe-prone David Coleman ("Moses Kiptanui; the 19-year-old Kenyan who turned 20 a few weeks ago," among many others) and now expanded to include verbal infelicities uttered on TV and radio by just about anybody, documents them fortnightly.

Last year's crop included a sterling, "Very unusually, it has turned noon here in Washington," from Huw Edwards, and an admirable, "Did your great-grandfather have any children?" from Fern Britton. In sport, David Pleat recorded a first-class, "When you've got a mountain to climb you may as well throw everything into the kitchen sink straight away" and Clive Tyldesley gave us "Gilberto Silva: does exactly what it says on the tin." In politics, David Cameron managed: "Every time I go to Iraq or Afghanistan, I'm blown away."

Another familiar trap is the camera that's rolling when the presenter thinks it isn't; BBC weather presenter Tomasz Schafernaker fell foul of that last year when he was inadvertently shown giving a one-fingered salute. But that's not really the problem here – although Deley did commit one or two fine Colemanballs, including: "And history in the making, as Oscar Pistorius from South Africa makes history." His issue is at once more simple, and more complicated: live television is a lot harder than it looks, and in its determination to "develop new presenting talent" and "showcase an innovative approach to live sport", Channel 4 let him find that out in the hardest way possible.

"I blame the channel, absolutely," says Des Lynam, for 20-odd years the effortlessly competent face of the BBC's sports coverage. "It was pretty dreadful to watch, but I feel sorry for the chap. He should never have been put in that position. Presenting a major live sports event is extremely difficult. You need a lot of experience of live TV, and you need to know your stuff on the sport. The first really major live event I presented was the Commonwealth Games in 1982. And I'd had 13 years of live broadcasting, a lot of it in sport, by the time I did it."

There's a world of difference, agrees the authoritative BBC cricket commentator Jonathan Agnew, a self-confessed "radio man", between presenting a live TV event and "knocking off a few recorded links to camera, then someone else stitching them together into a programme". He finds live television, he admits, "very hard. Very hard indeed".

For starters, it's a highly technical business. "You've got links to camera, links to your live commentators, links to recorded footage, interviews with studio guests," says Lynam. "And all the time, in your ear, you've got five different conversations going on. 'open talkback', it's called. It means you hear everything from the gallery. Not just what's intended for you. Producer, director, cameras, lighting, floor manager ... everything."

You learn to cut out the dross, says Jon Sopel, presenter of BBC1's Politics Show, co-presenter on the BBC News channel and a veteran of countless big live events and disasters (most recently the massacre in Norway). "But it's not easy. You've got 'Picking up on camera 2', 'Ready for overhead shot', 'Going to outside broadcast 1', 'Time to wind up', but you've also got: 'So, who d'you see down the pub last night?', and things you really wouldn't want to repeat in a family newspaper. And all the time you're trying to interview a cabinet minister."

Technical issues aside, there's the question of ease with yourself, Sopel says: "You have to have the basic confidence that when you open your mouth, words will come out and that they will make sense. You often have to sustain for a very long time on meagre material, so you need to have a few facts up your sleeve but you also have to eke them out – don't use them up at once."

What other advice do the experts give? Be natural, says Sopel. Talk normally. And when things go wrong, "admit it. People are quite forgiving if you don't try to cover up. Once we were covering Abu Hamza, I think it was, on his way to prison. We had a helicopter up, following this G4 prison van through the streets of London. I'd been talking for about half an hour and the van pulled over, the driver got out, went into a sweet shop, comes out with a packet of fags and lights up. It was the wrong van. Try extricating yourself from that on live TV."

Andrew Neil, who presents the live shows The Daily Politics and This Week for the BBC, says that, with experience, live is pretty easy – as long as all goes smoothly. "You earn your money when it doesn't. I once had to open an edition of Despatch Box with the words, 'Welcome to the programme. There's no autocue, the studio lights are off, and none of the guests has arrived yet. Other than that, everything's going swimmingly.'"

Some people – Neil included – claim to far prefer live television to recorded. Sue Cook, late of Nationwide, Breakfast Time and Crimewatch, says live is "so much more fun. Difficult, yes, you're trying to listen and make sense with one part of your brain, and talk and make sense with another, but people do admire you for it when it hasn't been a disaster ..."

Valerie Singleton, another legend, confesses to "absolutely adoring live. The tingle, the thrill of excitement you get when the little red light comes on. Perhaps I'm lucky because I trained as an actress; I once had to make up a whole speech in a play at Bromley Rep when someone didn't come on. But maybe it's not for everyone."

The absolute worst, all agree, the single biggest error to avoid at all costs, the ultimate no-no, is to embarrass your audience. Which, sadly, is what Deley did, albeit only a bit, and certainly not entirely through his own fault. "Live TV is a high-wire act," says Rageh Omaar, former BBC "Scud Stud", now with Al Jazeera English. "There's no middle ground. It's either seamless, or it falls apart in spectacular fashion."

Quite apart from "simply getting the mechanics right, which is hard enough", and "doing your homework, or at least having a decent hinterland, for when the 'rebel spokesman' turns out to be someone else"; quite apart from "being able to blot out five conversations in your ear, and talk for ages when there's nothing to talk about," you really need to be ready, confident, prepared, on top of things.

"The transition from studio to live is very difficult," he says. "The problem with Ortis is he was just dropped in at the deep end. He looked like a man on his own, with nowhere and no one at all to turn to. A man on the high wire, without a safety net."

And that, concludes Lynam, is unforgivable. "They could have made life easier for him," he says. "They could have given him an autocue for the main links to camera, so that at least was secure. They could have helped him by cutting away to cameras in the stadium when he was in trouble, so he could look at his script in peace. The direction really could have helped him. Honestly, I feel sorry for the guy."

Additional research by Sarah Marsh.