A finance worker collapsed and died after his body soared to 40C while running a half marathon in London, an inquest has heard.Kory Russell died from heat exhaustion after running the Royal Parks Half Marathon, finishing in front of the Royal Albert Hall.The 25-year-old, who worked as a financial officer at State Street Investment Management in Canary Wharf, had never taken part in such a long race before. However, he had completed races over shorter distances and had trained for the distance. He collapsed and suffered a fatal heart attack just before the finish line at the race on October 12 last year, Inner West London Coroner's Court heard. His father, Matt Russell, told the court that his son was a much-loved eldest child of four who had enjoyed maths and science and had been proud to take a job in London's financial district.His son, from Sully in the Vale of Glamorgan in Wales, loved swimming, football and running and had also worked in the kitchen of a Michelin-star restaurant in Penarth as he studied for his school exams.He had completed an economics and finance degree at Loughborough University for which he received a first-class grade. Kory Russell, 35, died from heat exhaustion after running the Royal Parks Half Marathon in LondonHe said his son had done Parkrun events and short distances with his girlfriend and friends prior to the event and had been looking forward to completing his first ever half marathon after meticulous training.Paramedics tried to treat Kory Russell at the finish line and performed CPR on him in a medical tent at the end of the race, Assistant Coroner Jean Harkin heard.They continued CPR in the ambulance as Mr Russell was taken to hospital. Cooling techniques were also used to reduce the impact of the heat exhaustion. Despite their efforts, he was confirmed dead by doctors at St Mary's Hospital in Paddington at 11.55am.More than 20 healthcare staff delivered the treatment for over 40 minutes - well over the 20-minute national guidelines of CPR before Mr Russell was confirmed dead.Mrs Harkin said: 'This time was extremely long and shows you just how committed the health services were.'An emergency doctor who was at the scene, Edward Langford, said: 'The priorities of care were ice water cooling to reduce the temperature and chest compression with a Lund University Cardiopulmonary Assist System (LUCAS) machine.'However Mr Russell's core temperature remained over 40 degrees celsius, despite the treatment from paramedics. He had no previous history of heart problems and was not on any medication. He was last at the GP for muscular upper abdominal chest pain in 2022, where he took a blood test which came back normal.There was no ethanol or alcohol in his blood or urine following post-mortem tests.Doctors agreed his death was a case of sudden cardiac arrest in a young man with a normal heart.A GoFundMe page set up by Mr Russell's family raised £1,290 to support the Sudden Death charity, SADS UK and the CUBE centre in Barry.The introduction to the fundraiser said: 'Kory gave so much to others - let's show his family they're not alone.' Mr Russell's core body temperature soared to 40C and would not come down even as paramedics tried cooling down measuresSince her son's death, his mum Rhi Russell, stepped into the Vice President role at Calon Hearts UK, a charity which runs cardiac screening programmes.She previously told Metro: 'Kory was the kindest, most loving and hard-working person you could ever meet.'He gave everything his all, whether it was work, sport, family or friendships. He had such a big heart and a personality that would light up any room.'We are all heartbroken. He will be forever missed and remembered with endless love.'She now supports current President Ruth Macdonald, who also lost her son Ben as he collapsed at another half marathon from a sudden cardiac arrest.They launched the Screen Early, Save Lives campaign inspired by the pair.At the time of Mr Russell's death, The Royal Parks Half Marathon said: 'Everyone involved in the organisation of the Royal Parks Half Marathon would like to express sincere condolences to Kory's family and friends.'Mrs Harkin concluded that Mr Russell died from a cardiac arrest caused by heat exhaustion.