Thousands of runners in a popular half marathon have seen their finishing times take a hit after organisers revealed the course has been too short for the past three years.
An inquiry was launched after Brighton runners reported that data recorded on their tracking devices failed to measure up to the 13.1-mile distance.
UK Athletics contacted Brighton half marathon organisers following concerns about last month's race, and it has emerged the course had fallen short by 146m since 2015.
The area of concern centred on a turning point just after mile four where the course passes the independent Roedean School before turning and heading back towards Brighton.
In a statement, Brighton half marathon said: "We have concluded that the eastern turning point has been positioned incorrectly over the last three half marathons, resulting in a shortfall in the overall half marathon distance.
"We are devastated that this mistake has happened and apologise unreservedly to all runners who took part in the affected race years."
The news means that runners face having their personal bests, records and race times affected. And officials admitted the error was likely to have overshadowed the event for many.
DJ Norman Cook, aka Fatboy Slim, launched this year's marathon, marking the 27th year of the race, which raises funds for the Sussex Beacon, supporting an HIV care centre in Brighton.
Race director Martin Harrigan said: "We are a team of runners ourselves so we fully understand the impact of this news. We are really upset that this mistake has happened and we take full responsibility for this situation."
Simon Dowe, CEO of the Sussex Beacon, which organises the race, said: "We can't apologise enough for this mistake. I know it's hugely disappointing to everyone who trained so hard."
Some runners called on organisers to offer a refund or a discount for next year's half marathon. Others questioned why the course length had not been checked following concerns raised last year.
And some runners said their half marathon personal best times had been tainted by the revelation, while others voiced annoyance as they had only run it in order to qualify for another race.
Brighton Half Marathon elite race winner Eleanor Davis, who set a course record of 74.26, spoke of her frustration as she only competed to gain elite entry for the London Marathon.
Ms Davis, of Newquay Road Runners in Cornwall, said: "The reason I ran the race was specifically because there was a deadline to get a qualifying time for the London Marathon.
"I knew I was capable of getting under 75 but I needed to pick the right half marathon, so I choose the Brighton Half Marathon, and trained at altitude for three weeks.
"To find out afterwards that it counted for nothing was pretty devastating and concerning. But luckily, the London Marathon have been really kind and waivered it for me so I can compete."