Double Olympic gold medallist Shirley Robertson was forced to retire from day two of the Extreme 40 iShares Cup at Cowes Week after a collision with a spectator boat.

Robertson – who was skippering the iShares boat – had been on the race course for just three minutes when the collision happened – which threw crew member Dee Caffari overboard and left a spectator requiring hospital treatment.

The crash forced Robertson to retire with a broken gennaker pole and damage to the bow after the first of the day’s eight races.

“It was really disappointing to have the day cut short after only the first race. I only got wet but we were all upset to hear someone had been hurt,” said Caffari.

Crews had complained before racing started about ribs straying on to the race course - but officials were powerless to act as racing got underway.

"We can only advise people to keep off the course but we will have to have a look at it," a spokesman said.