​A former soldier is preparing for what he calls “the longest run home ever” as he gets ready to run from Beijing to London in memory of his grandad.Jack Jarvis from from Hamble, Hampshire, will cover about 31 miles (50km) every day for eight months, crossing 18 countries, and completing the equivalent of more than 300 marathons.AdvertisementAdvertisementAdvertisementThe challenge starts on Monday at Tiananmen Square and will finish at Trafalgar Square in March.The runner will raise awareness and funds for the charity Brainstrust, in honour of his grandfather who died from brain cancer in 2007.”If I want people to donate their hard-earned cash to me, I want to do something big so they feel like they’re getting their money’s worth,” he said.Jarvis said he would aim to consume about 7,000 calories a day, and plans to sleep and recover in a transit van driven by friends that will be travelling alongside him on the route.Kazakhstan, Greece, Serbia, and France are among the countries he will have to cross on his journey home.AdvertisementAdvertisementAdvertisementThe former 59 Commando Regiment soldier said the challenge “will push the limits of what’s possible, physically and mentally”.Jarvis is no stranger to pushing his body to its limits, breaking a Guinness World Record in 2022 by becoming the first person to row across the Atlantic Ocean from mainland Europe to mainland North America non-stop.In 2023 he was involved in a skydiving accident, which seriously injured his leg and led to more than 18 months of rehabilitation.”After my accident, I had to rebuild everything,” he said.Adding that his latest fundraiser was “the ultimate test of that journey”.AdvertisementAdvertisementAdvertisementReflecting on all of his challenges, he said he had taken them on in memory of his grandfather who died from brain cancer.The former pub landlord from Hamble was the “life and soul of the party” Jarvis said.According to Brainstrust brain tumours are the biggest cancer killer of children and adults under 40 and more than 102,000 people in the UK are currently living with a brain tumour.Jarvis has set his fundraising target at £1m, which Brainstrust said, if achieved, would double its ability to give personalised support to 10,000 people a year.Record-breaking rower survives parachute disasterSolo rower completes Atlantic challenge