There was the usual diversity at the London Marathon last year: Starship Troopers, Santas, a Pope, a gingerbread man, a rhinoceros, various Duchess of Cambridge lookalikes and a 23ft-high giraffe, all in running shoes.
What spectators are less accustomed to seeing, among the ranks of competitors in fancy dress and the middle-aged club runners, are participants under the age of 25. Marathon running in Britain is widely seen as something you take up after the big three-zero; a chance to raise money for a favourite charity or a physical challenge to confront midlife crisis and fight the ageing process.
Venetia Marriott, 23, from Mitcham, south London, is trying to change that stereotype. For the past year she has been using running as a therapy for coping with the loss of her father, who died from cancer. She never expected to be attempting the London Marathon so quickly. "It's one of those things that you've got in your plans – I didn't think it would come so soon. Whenever you watch the marathon on TV there are very few people that represent my demographic as a young black female." Marriott's training schedule, documented on Twitter and Instagram, has encouraged friends to follow her example.
Another of this year's participants, Elizabeth Lawoyin, 21, took up running as a New Year's resolution. Few of her friends thought she would stick with it. "I think the attitude was that I would give it up after about two weeks." She found it difficult to run alone – "it gets really tedious" – but then, like Marriott, she joined the London-based club Run Dem Crew, which brings together runners of different generations and backgrounds. She signed up for a 10km run in London but had to adopt a new lifestyle. "I've become very, very disciplined. I've realised that it's not that we don't have enough time, it's that we are not disciplined with our time."
As Lawoyin, from Edmonton, north London, has done more race challenges, from the "absolutely beautiful" Kent Coastal half marathon to the Paris half marathon, so the scepticism among her friends has vanished. She runs without technological distractions. "We don't really spend time with ourselves – we spend time with our phones. When you run it's just your mind and your body and you think about things. "
With its catchphrase of "Leave it on the road", Run Dem Crew encourages the philosophy of using running to relieve stress. The communal format is an opportunity for young runners to break out of the postcode restrictions of some of Britain's gang-infested urban areas and meet people who can open their imaginations to career paths they had never previously considered.
Run Dem Crew's members include graphic designers, teachers and media-agency owners who do their weekly runs alongside the "Youngers". On marathon days, a "Cheer Dem Crew" will gather at the 21-mile marker to support colleagues and all other runners. Among the cheering group will be Youngers who might run 26 miles next year.
Charlie Dark, the founder of Run Dem Crew, says it has been a challenge to get the young runners marathon ready during one of the coldest winters in memory. "But it's good for them to get out and experience the elements rather than be at home on the Xbox," he says. "If you train when the weather's bad it means you can train anytime."
The Youngers taking part in the Marathon are also being supported by Youth Net, an online support service for young people. They have agreed to share their marathon experiences with Youth Net's users, many of whom come to the website when they have problems. Emma Thomas, Youth Net's chief executive, said she hoped many would be encouraged. "For many young people it's about giving them something to focus on, it gives them something positive."
For Thomas Crosbie, 24, marathon running has been a means of bringing his life back on track after childhood dreams faltered. As a teenager he was championed by the Poetry Society and performed his work in Trafalgar Square and the Globe theatre. He visited Downing Street and appeared on Blue Peter with Ms Dynamite. A good middle-distance runner, he competed at English schools level. In adulthood, Crosbie found things tougher. "I needed some direction – I had come out of a period of not knowing where I was or what I wanted to do."
Joining Run Dem Crew has given him confidence. "It was less about winning and more about sharing the enjoyment of running." He has found a part-time job with children with behavioural difficulties and is recording an EP of his rap poetry with the accomplished jazz drummer Seb Rochford. And he is running the Marathon. One friend told him he was getting "too old, too quick". But Crosbie doesn't see it like that. "There's an endorphin rush, a buzz," he says. "I feel I now know who I am and what I'm about."
For more information go to rundemcrew.com
The London Marathon
* Next week's race will see around 30,000 men and 18,000 women donning their lycra shorts and trainers to raise money for charity.
* The event will be an especially important day for a small group of 163 runners who will also be celebrating their birthdays
* The oldest runner taking part is 88-year-old Paul Freedman.
* A grand total of 1,521 teachers will be setting off after the starting pistol, the largest group by occupation.
* They will be joined by 366 City bankers.
* There will be 300 metres of blue paint used to mark out the route around the city.
* There are 7,200 blogs being written by runners taking part.