A seven-year-old from Sheffield is believed to be the youngest person to complete the coast-to-coast cycling challenge.
Noah Elgar, from Greystones, cycled more than 90 miles between Bowness-on-Solway, on the west coast near Carlisle, and Tynemouth, on Britain's eastern shores in Newcastle.
The plucky youngster completed the gruelling route in three days, arriving in Tynemouth on Wednesday afternoon.
He was accompanied by his dad Tim Elgar, 13-year-old cousin Rhys Schofield and aunt Jackie Schofield, with his three-year-old sister Jemima joining them for the last five miles of the epic journey.
He has raised more than £1,500 to be split between two charities: The Snowdrop Project, in Sheffield, which helps victims of modern-day slavery; and e:merge, a youth charity in Bradford.
"It was quite hard, especially the second day when there were lots of hills, but I feel good having done it," said Noah.
His father Tim said he was not aware of any official list of the youngest people to have cycled coast-to-coast but he had been unable to find reports online of anyone younger.
"Noah's always been naturally fit. He does park runs, loves riding his bike and was looking for a challenge, so we thought why not?" he added.
"There were quite a few doubters, including my mum, who thought we'd have to bundle him into the car at some point.
"But he completed it all under his own steam, with only a couple of minor crashes on the way, and I think people have been really inspired by what he's achieved."
Lara Bundock, chief executive of The Snowdrop Project, said Noah had raised a life-changing amount of money, which would pay for one victim of modern-day slavery to receive five months of trauma counselling.
"I'm so impressed he was willing to put himself through a challenge like that, which is something I certainly couldn't do," she added.
"The fact someone so young is engaged with modern slavery, and wants to do something to prevent people being exploited, gives me a lot of faith in the generation we're bringing up."
* You can still donate online at https://mydonate.bt.com/fundraisers/timelgar5.
* The Snowdrop Project is organising its own sponsored coast-to-coast cycle ride, which will take place on May 5 and 6 next year over an even more challenging 140-mile route.
It is seeking around 25 participants for the challenge, which is being sponsored by the Co-op.
Full details are due to be announced on September 12, but in the meantime, anyone interested can email the charity at firstname.lastname@example.org.