The organisers of the Brighton Half Marathon have apologised after the course for the past three years turned out to be almost a tenth of a mile short.
They carried out checks after some runners claimed that it was too short and others that it was too long.
The event is the biggest fundraiser of the year for the Sussex Beacon but also attracts many serious runners.
Today (Friday 28 march) the organisers said: “Earlier this month Brighton Half Marathon was contacted by UK Athletics following concerns regarding the length of this year’s course and the course in 2015 and 2016.
“Over the past few weeks we have been conducting a formal investigation into this matter and can now confirm that unfortunately the course has been short by 146 metres (0.09 miles) for these particular race years.
“The area of concern centred on the turning point just after mile 4 where the course passes Roedean School before turning and heading back towards Brighton.
“UK Athletics’ concerns were not observational regarding the course layout but were based on an analysis of GPS data.
“The accuracy of GPS devices is a hot topic within running at the moment, with some runners reporting variances for the race both under and over the correct half marathon distance.
“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.”
Sussex Beacon chief executive Simon Dowe said: “We can’t apologise enough for this mistake. I know it’s hugely disappointing to everyone who trained so hard.
“I also know that for some, the news will be devastating as it affects race times, personal bests and records.
“Our thoughts are very much with the runners. I’m so sorry that their remarkable achievements and the money raised for good causes may be overshadowed by this error.”
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.
“We remain committed to making the 2018 Brighton Half Marathon a great event.”