Collett has been selected for three
European Eventing Championships as an individual. She was eliminated on the cross-country on her senior championship debut at Luhmühlen in 2011, but finished 13th at the 2015 championships at
Blair Castle on Grand Manoeuvre. Collett was second at
Luhmühlen five-star in 2018 on Mr Bass, but she achieved her first five-star win in October 2020 when she took the title at the
Pau Horse Trials, France, riding her own, Keith Scott and Karen Bartlett's horse London 52 and therefore has the honour of winning the only five-star of 2020 because the eventing calendar that year had been decimated by
COVID-19. The horse had previously been the 2018 eight- and nine-year-old champion at
Blenheim Horse Trials, as well as winning the Event Rider Masters at Chatsworth Horse Trials and the CCI4*-L at the Boekelo Horse Trials, both in 2019. But he had also fallen at the 2019 European Eventing Championships in Luhmühlen having sat third after the
dressage. In 2021, eight years after her near-fatal accident, Collett and London 52 were selected to represent Britain at the
2020 Summer Olympics in Tokyo that had been delayed by the
COVID-19 pandemic. She won gold in the team event with
Oliver Townend and
Tom McEwen. Collett was appointed
Member of the Order of the British Empire (MBE) in the
2022 New Year Honours for services to equestrianism. In 2022, Collett won the
Badminton Horse Trials. Riding London 52, she led from start to finish, setting an all time Badminton record finishing score of 21.4. In June 2024, she was confirmed as part of the Great Britain team to compete at the
2024 Paris Olympics on London 52. She won gold in the team event with
Rosalind Canter and Tom McEwen. In August 2025, she was selected for the British team for the
2025 European Eventing Championships held in Blenheim on London 52, riding alongside McEwan and
Yasmin Ingham from the 2024 Olympic squad as well as
Bubby Upton and
Caroline Harris. She won the individual gold medal on London 52 at the event, although the British team suffered from falls by Ingham and Upton in the cross country section. ==Personal life==