Meet George Grassly, the world’s fastest accountant who runs 200km a week

“I have either massively cooked this,” George Grassly thought as he crossed the halfway mark of the 2026 London Marathon in 65 minutes and 16 seconds. “Or something quite special could happen.”

Just over an hour later, Grassly became the 10th Brit across the finish line, winning the mass category. His 2:12:54 was not only almost two minutes faster than the second-placed amateur, but the fastest London Marathon mass time on record, clearing the previous mark by 24 seconds. This was his second marathon, having made his debut with a 2:21:17 in London last year.

Many who followed him up Pall Mall are either “runfluencers” or professionals in other distances or disciplines, while Grassly is a 25-year-old accountant at PWC with a first-class master’s in engineering from Durham. His marathon training block – January to March – was also “busy season” at work, regularly clocking 10- or 11-hour days. “I was running in the dark the whole time basically,” he says. “I just wouldn’t really see much natural light.” Sprinter Eugene Amo-Dadzie calls himself the “world’s fastest accountant”, although Grassly is challenging that title.

Before his training block began, Grassly was averaging about 150km weekly, although without marathon-specific sessions. From January, his average training week comprised 12 runs, averaging about 200km in total. Nine of these were “easy” runs (averaging about 4:45 per km); often the 10km commute from his Fulham home to London Bridge office, expanded to 14km by running along the Thames. On Tuesday evenings and Thursday mornings he trained with a club – Cottage Relocated, an elite distance group – also running to and from Battersea Park for those sessions. Saturday mornings were for his main training run – often significant distance at his marathon goal pace – while Sundays were an “easy” long run.

“With marathon training you’re kind of putting your body on the edge the whole time, risking either getting injured or it clicking,” he says. “I really should have done so much more strength work for what I’m doing, but while I’m working and trying to have a bit of a social life, two gym sessions a week is the bit that gets parked. It’s just been pretty intense, and I’ve been pretty tired the whole time, but I managed to hold it together.”

Grassly started running seriously around the end of primary school, earning a running scholarship at Harrow by 13. He competed over the next five years, developing into one of the country’s most promising long-distance runners. While he continued running in his first two years at Durham, it eventually fell away.

“I enjoyed uni life far too much,” he says. “My body was just changing, and I kept getting injured and didn’t really recover from any of them properly. After a couple of years of that I just played a bit of college sport, and then in my first couple of years in London I continued that uni lifestyle.”

In October 2023, he ran the Royal Parks Half without any formal training (still finishing in 1:18) and in early 2024 he started training more regularly with his girlfriend. “In our first year together she did the Paris and London Marathons within two weeks. We did a bit of training together and that motivated me to get back running properly.” The Hackney Half followed in May, and from there he joined a training group, targeting London the following year. Throughout most of 2024 he was still averaging only 30km per week, a figure which quintupled through the same period in 2025. But the biggest change was joining Cottage Relocated, which meant he was “training with people who are better than me”, getting “dragged round sessions” but “improving quite quickly”.

For fuelling, he prioritises volume and listening to his body over eating specific foods, and a sweat test taught him always to have water with electrolytes on the go. He only went tee-total for the month before the marathon, trying to maintain his normal social life wherever possible, although after-work drinks went out of the window. He trained with gels wherever possible, having endured stomach issues at London 2025, taking on a gel every 20 minutes during the race, 90g of carbs per hour.

The obvious question is whether he plans on going pro, but he says “unless a ridiculous opportunity, a ridiculous brand deal came around, I wouldn’t do it yet. I’m not quitting my job any time soon.” He acknowledges the need to play the social media game and has gained 5,000 Instagram followers since the race – “Long gone are the days of being supported just for running quick” – although he was backed by Hoka, the shoe manufacturer, for London 2026.

“If it’s something you want to be good at, just try and look for the wins,” he says. “I just love working towards a goal. Don’t get me wrong, there are so many runs that I do which I really can’t be bothered, but I have in the back of my mind that I want to run really quick, I’m targeting this, I need to do this.”

By the time we spoke on Thursday, Grassly had just finished his second 5km run since the marathon, despite being on a truly well-deserved holiday in Egypt, and will take on Hackney Half again in two weeks. From there he will work towards another marathon later this year, most likely Valencia in December, where he would line up with the elites. “It seems crazy to say, but the next barrier is a sub-2:10.”

Photograph by Scott Steel-Morris