10k race course prankster
A course sign that was taken from the race is seen on the ground. Acorn Trails

Runners taking part in a 10k race in Scotland were sent on a long detour when a woman pretending to be a race marshal hid arrow signs and sent them off of the course.

It happened near the end of the Acorn Trails race in Glasgow on Sunday.

"I'm left with some bitterness, anger and disappointment," organizer Alex Osbourne posted on Facebook.

The woman took down a large route arrow and then moved a smaller one to change the direction of the route. They then imitated a marshal and pointed runners in the incorrect direction.

"The pettiness endangered runners taking them away from the safety of a marked and marshalled course, and forced them further into the park, towards the road and away from any first aid provision they could have potentially required," Osbourne said. "It makes me rather angry that anyone could be so reckless."

He apologized for not having a real marshal at the spot and offered a 50% discount for the next race to anyone affected by the prank.

"It's hard to factor in interference from mischievous folk, and this was a spot we didn't think would have such an issue," Osbourne said.