They are beloved by holidaymakers and better suited to the calmer waters of the Med.

But now four intrepid fundraisers are preparing to travel 500 miles around the treacherous northern coast of Scotland in a pedalo designed to look like the Loch Ness Monster.

Ed Foster, Nico Kirby, his sister ­Natasha Kirby and Sholto Morgan will set off from Inverness before heading out into some of the UK's most dangerous waters for Cancer Research and Parkinson's UK.

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Their route will take them down the Caledonian Canal, through Loch Ness and Loch Lochy and out into the Irish Sea. They will head north to Cape Wrath, east to Thurso and round John O'Groats before pedalling back to the Highland capital.

Mr and Ms Kirby lost their mother, Antonia, to lung cancer. Ms Kirby, 28, a banker, said: "What we are doing is completely mad and has never been done before.

"But that's part of the thrill of something like this."

A support boat will follow them and they hope to raise £250,000.