Two young dog walkers had the surprise of their life when they spotted a pair of killer whales circling their prey off Bacton in north Norfolk.

Toby Beatty, 14, was first to spot the fins and alerted his sister Jessica, 15.

They were walking along the beach at about 7pm on a gusty evening last week. From their descriptions of the fins, the backs of the animals and their behaviour, the marine research charity Sea Watch was able to confirm that they had seen killer whales.

Jessica said: 'Toby said there was something in the water. I did not believe him, but then I looked over and the fins were huge. There were two large ones which looked like they were circling a smaller one.

'We watched for a while and the smaller one seemed to swim away, then I ran back home to alert my mother who is a member of British Divers Marine Life Rescue, but she had gone out. By the time I got back, the fins had gone too.'

The family moved to Bacton a month ago from Wells.

Sea Watch director Peter Evans said: 'Interestingly, there was another sighting of two killer whales, possibly the same animals, at Humberston Fifties off the Norfolk coast, by Dick Lorrand two days earlier on the 17th. Killer whales rarely enter the southern North Sea. It is possible they were in the area in pursuit of common seals, which form part of their diet.'

Jessica and Toby's sightings come on the eve of National Whale and Dolphin Watch, hosted by Sea Watch and sponsored by BG, from July 27-29, and the charity is hoping there might be further sightings in the area of the whales as well as sightings of other species such as harbour porpoises and white-beaked dolphins.

Anyone can take part by downloading and sending in sightings forms from a point on the coast near them, by joining public watches which are being held around the coast, including at Overstrand on July 28, or by going out with accredited boat operators.

Full details of how to take part are available at www.seawatchfoundation.org.uk