One night, when he was just 15 years old, Sebastian Green and a friend took a boat from Weymouth Marina without the owner's consent and went joyriding in the Fleet Lagoon behind Chesil Beach. They eventually ran aground, and when Seb leapt over the side to walk ashore, he sank up to his waist in mud and stuck fast...

His subsequent rescue involved the coastguard helicopter, an inshore lifeboat and an overnight stay in hospital. He estimates the bill for this teenage prank gone wrong was approximately £20,000.

On 1st February 2008 18 year-old Seb set out from Weymouth with just his dog for company in an attempt to walk round Britain. His intention was to raise £20,000 for charity - a sum equivalent to the cost of his rescue. He arrived back on Sunday 14th December 2008 having walked over 3,500 miles.

This is his story.