Britain’s Beth Potter ran the second-fastest road 5km ever by a female athlete at a race in the Lancashire village of Barrowford.
Scottish runner Potter, 29, who competed at the 2016 Olympics, clocked a time of 14 minutes 41 seconds on Saturday.
The time may eventually be classified as a world record.
“It was really good to get a race in the early season but that was beyond my expectations,” Potter said.
“It all started to sink in when I had about a kilometre to go and I saw the clock said 11 something and I was trying to do the maths in my head, I was convinced the clock was wrong, I couldn’t believe it,” she told BBC Radio 5 Live.
Only Kenya’s Joyciline Jepkosgei has ever run faster – recording 14:32 during a 10km race in Prague in 2017.
However, 5km road racing has only been recognised as an official world record event since January 2018, meaning Potter may have set a world record time.
That mark is currently held by steeplechase world champion Beatrice Chepkoech, who ran 14:43 at the Monaco Run in February.
Whether Potter’s time at the Podium 5km event is eventually ratified as an official world record by World Athletics depends on a variety of rules such as the presence of anti-doping officers, the size of laps and the accuracy of the course measurement.
After making the move to triathlon four years ago, Potter said she hoped to be competing at the 2020 Tokyo Olympics but she missed out on selection.
“It’s frustrating because I feel like I’m an in-form athlete at the moment,” she said.
Potter finished 34th for Great Britain in the 10,000m at the Rio 2016 Olympics before switching to triathlon, winning gold at the 2019 European Championships.
Elsewhere, Kenya’s Ruth Chepngetich smashed the world half-marathon mark in Istanbul on Sunday.
The 26-year-old took 29 seconds off the world record with a time of 1:04:02.