Bill O’Connor is a member of a very elite group. The Queen’s Park Harriers runner is one of only 15 people worldwide to have participated in every London Marathon since its inception in 1981. On Sunday, he will take to the capital’s streets for the 34th time.

His target? “I’d just like to finish,” the 68-year-old from Hokitika in New Zealand says. “Somewhere around the five-hour mark. It would be faster, but my leg has been playing up for the last few years.

“It feels good to be part of that group. Originally you got into the London Marathon on qualifying times, which was two hours 45 minutes or better.”

In 1995, O’Connor and the other runners who had completed the first 15 London Marathons – at the time, there were 42 men and women – were guaranteed entry every year. They were the ‘Everpresents’ of the world’s leading marathon.

“After the 15th year, the organisers said if you could prove you had run the first 15, you had a place for life,” says O’Connor. “The group has been whittled down over the years to 15. I’ll keep going as long as I can!”

O’Connor, a teacher at Queen’s Park Community School who lives in Finchley, moved to London more than 40 years ago, when he took up a role as a maths teacher.

It is fair to say running is in his genes – his sister Mary was an Olympic marathon runner and his brother ran the Pakistan National in 2:21. “He’s 62 now and he’s still running three and a half hours – I could beat him if my leg was right.”

Prior to leaving New Zealand – for a dare by one of his friends – O’Connor was already well-known back home, having run in the former Great Westland Marathon.

He was in illustrious company, training at Greymouth Harriers Athletics Club alongside Dave McKenzie, who went on to win the Boston Marathon in 2:15. “It was an American record at the time, and he ran it in a snowstorm.

“At the time, Greymouth was producing an incredible number of national athletes. Most of my mates were playing rugby league for New Zealand.”

O’Connor’s contribution to teaching was recognised when he was given the chance to carry the Olympic Torch ahead of London 2012.

He is now training for his latest marathon effort, pounding the paths of Hampstead Heath every night.

Unsurprisingly, O’Connor has seen plenty of changes over the last three decades, both to the landscape of the capital and the standards of the competitors. “I’ve seen the London Marathon grow from nothing,” he says.

“When the first one took place there were only about 6,000 of us. Now there are almost 40,000.

“There were no high-rise buildings in London. Canary Wharf didn’t exist. There was no Docklands Light Railway. No Olympic Stadium. You could have bought the whole lot for a couple of quid. And now that’s where all the crowds are.

“The standard has dropped. There are more people running it but the standard up front is not as high as it used to be. Back in the 80s we just considered ourselves club runners, but if I was running those times today I would be in the top 100.”

O’Connor has advice for anyone considering taking part in a marathon: “Join a club and get used to racing and training. Running with others makes it a lot easier. You learn about pacing, sprint training, all the little things that make you better.

“A lot of people these days do the marathon without doing any of the other stuff, but the marathon should be the last thing you do. If anyone wants to do a marathon then do the big city ones like London, because if you come unstuck there is always someone there to help you.”