That broke his previous Irish U-20 record of 45.85 and brought him home well clear of France’s Milann Klemenic (46.44) and Czechia’s Ondrej Loupal (46.62).

Kelly is the ninth Irish athlete to have won gold at the European U-20 Championships, which date back to 1970, with Elizabeth Ndudi the most recent winner before him, the Dubliner taking long jump gold in 2023. His time moves him eighth on the Irish all-time list.

“An incredible day at the office,” said Kelly. “I need a bonus – I’m working overtime here. I just want to enjoy this achievement. It’s taken a lot of work and I’m so proud.”

Kelly had gone into the championships as the favourite and the Finn Valley athlete, who broke the Irish U-20 record indoors with 46.54, proved a class apart throughout, winning his heat in 46.94 and his semi-final in 46.58.

Kelly was born and raised in London to Irish parents – his mother Mary-Jo hailing from Derry while his father, Steve, was born in Lisburn and grew up in Dublin. Last year, he smashed the Irish U-18 400m record to win bronze at the European U-18 Championships in Slovakia and then helped the Irish men’s 4x400m team reach a final at the World U-20 Championships in Peru.

“Last year’s bronze was great, but it hurt me,” he said. “There’s such a huge amount of work you have to put into this: food, going to bed early. There’s so much day-to-day work at 100 per cent. My coaches, dietician, physio and all the people around me – it’s a big team. This feels amazing.”

Sean Doggett was also in action in the 400m final, finishing seventh in 47.16, while earlier in the evening, Precious Akpe-Moses – the younger sister of former European U-20 100m champion Gina – finished fourth in the women’s 200m final, clocking 23.72 (-2.0m/s). Gold went to Germany’s Judith Bilepo Mokobe in 23.40.

“The bend was so good and then I just think after all six races I’ve done, I might have lost it a bit,” said Akpe-Moses, who finished seventh in the 100m final on Friday. “But I’m okay with where I came. Fourth in Europe was the best I could do, so I’m content.”

Akpe-Moses returned to the track soon after to help Ireland to second place in their heat of the women’s 4x100m, clocking 45.27 to automatically advance to Sunday’s final alongside Fatima Amusan, Molly Daly and Leila Colfer. Switzerland took victory in 44.63.

Cian Crampton had a strong showing in the men’s discus final, the Edenderry athlete throwing his leading mark of 57.76m in the final round, which was good enough for sixth, with gold going to Dutch athlete Jarno van Dalen with 63.18m. “I would have liked a bit more but I can’t complain with sixth,” said Crampton. “I was looking for a medal, but it didn’t work out in my favour.”

Dubem Amah was “over the moon” to reach the men’s 200m final after clocking 21.30 in his semi-final. The 17-year-old Tallaght sprinter went on to finish seventh in 21.76 into a stiff headwind (-2.9m/s), with gold going to Italy’s Diego Nappi in 20.77.

Cormac Dixon came home ninth in the 3000m in 8:48.27, while the Irish men’s 4x400m team of Alex Cullen, Andrew Hayes, Ethan Dewhirst and David Davitt fell short of the final after clocking 3:12.28 to finish fourth in their heat.