A 17-year-old known as The Hull Boy has described becoming the youngest person to run the entire length of the UK as "surreal".
Marcus completed the journey from Land's End to John O'Groats on Thursday.
After raising about £130,000 for a mental health charity, he said the 58 days of running had been "the best months of his life".
Marcus – known to his large online following as The Hull Boy because of his love of Hull City FC – is the first person under 18 to have completed the adventure.
The teenager, who lives with his parents in Malton, North Yorkshire, has openly talked about his struggles with his physical and mental health.
"At the age of 15 I attempted to not be here any more," he said.
"I was 145kg [22.8 stone], diabetic, struggling badly with depression, anxiety and OCD."
As a young carer for his father he felt unable to speak out about his own struggles, so he said he bottled up his emotions.
Marcus started to run one mile a day before taking part in his first marathon in September, accompanied by his friend Russ Cook – known as the Hardest Geezer – who made global headlines after running the length of Africa.
Inspired by Mr Cook, he said his dream was to run the length of the UK, and he hoped to raise £20,000 for the mental health charity Mind.
Marcus said the journey was "very tough" and that at times it was wet, dark and a "lonely adventure".
But there were also some unforgettable moments, from running alongside deer to enjoying amazing sunrises and sunsets.
He said that running for a good cause brought people together.
"It's been beautiful. The last few weeks have been surreal," he added.
Celebrity attention
His challenge caught the attention of celebrities, and on day four of the run he received a special message.
Four-time Olympic medal holder Sir Mo Farah posted on social media saying: "Keep going champ! Anything is possible."
Former NFL star JJ Watt also sent a message, saying: "Just over a year ago, you began a journey to change your life and along the way, you changed the lives of so many others."
Marcus said he met many "incredible" people along the way but one of his best moments was when someone drove four hours to find him on the road and share their story about mental health.
Appearing on BBC Breakfast on Friday, he told Naga Munchetty and Charlie Stayt that he went to use the toilet at a supermarket thinking he had raised £70,000, but by the time he came out he realised he had raised £100,000.
He said he would now be doing nothing for a few days apart from resting and spending time with his family and dog Bruce.
Hull and East Yorkshire on BBC Soundslatest episode of Look North here.
