The incdient happened after they moored the 24 foot long Little Stint near Grace's Lane Little Baddow [Essex, England] last week.

They described their fearful experience involving flashing lights, thrown gravel and footsteps on the cabin roof to Blackwater Boats proprietor, Ron Abbott next day.

"I told them of the legend of Grace's Ghost a young woman who drowned in the river more than 100 years ago. They had never heard of it but they were obviously very frightened by their experience.

"They said the lights were like torches shone through the windows and could not have come from cars on the A12.

"They could see nobody and I confirmed there was no gravel in the vicinity to be thrown or scrunched underfoot.

"They said they burst out of the cabin to try and catch whoever was walking on the deck and cabin roof but there was nobody."

Chelmer Canal Trust's John Marriage, also a writer and historian, said:"It was mysterious and terrifying for the young couple. There are numerous reports of sitings on this old track and the bridge that crosses the river.

"The woman has been said to ride a horse and wear a cloak. I am not sure whether the legend is 17th or 18th century but it is well-documented and there have been witnesses in living memory. This river story is facinating."