He completed his 240th marathon on Saturday to reach the most 26.2 mile runs ever completed by a single runner in a calendar year.
His world record breaking feat happened after taking part in the Dunstable Marathon.
But rather than resting on his laurels he now wants to complete 400 before the 365 days are up.
Mark, who grew up in Shrewsbury after being adopted, is pushing himself to the limit for Adoption UK
"People keep congratulating me on the record but I feel like I'm sitting in a room that has been half wallpapered," said Mark, who works as a fitness trainer and window cleaner.
"Everyone keeps coming in to see how great it is but I know there is still more work to be done.
"It sounds strange but I try not to think about things like breaking the world record, because I have so much else going on.
"I let other people think of that and I just run.
"Having said that, I am aware it is something I should be proud of and I certainly do feel a great sense of pride.
"I was talking to my manager recently and we were talking about how far this whole thing has come, it is surreal."
"It might sound sad to some people but my body is just used to it now.
"My trainer believes I am conditioned now to do 26 miles of running a day.
"It also helps that when I feel like I may be hitting a brick wall, I can think of the good cause I am doing all of this for and that will keep me going."
Mark also wants to run four marathons in 24 hours and then 50 marathons in 50 states in just 25 days.
He plans to run the four marathons in just 24 hours next week, starting from his home town and finishing at the Iffley Road track in Oxford.
It was where Roger Bannister first broke the four minute mile and fittingly Mark has been invited to complete a lap of the famous track.
Then he not only wants to travel to America to run 50 marathons in 50 states, he wants to beat the benchmark set by ultramarathon runner, Dean Karnazes, by completing it in half the time, which is 25 days.
Perhaps his biggest challenge will be trying to out-do Andrew Rivvet, who ran from Land's End to John O' Groats in nine days, two hours and 26 minutes on March 24, a record which has stood since 2001.
Steve O'Brien, who has coached Mark for the last year, said: "Biomechanically, he's just built differently to anyone else.
"The American challenge is a no brainer and he can definitely to that one but the Land's End to John O'Groats run will be the hardest yet.
"That's a real test of human endurance and has the potential for Mark to topple over," he said.
"He's going to be on his feet for 18 hours a day for more than nine days.
"But Mark just loves to run and wants to push on to 1,000 marathons.
"He is able to do that without suffering injury because his make up is different to anyone else's."
The grief of the six miscarriages suffered by his wife Tammy inspired him to tackle a marathon every day over the summer.
But, having reached his goal in style, he was still not satisfied, so he is now pursuing the dream of 400 marathons in 365 days.
He has set himself a target of raising £90,000 for the Tommy's pregnancy charity and Katharine House hospice in Stafford.
He can be found on Twitter @400in365 and anyone who would like to sponsor him during his challenge can do so by visiting his Virgin Money Giving page – '400 marathons in 1 year'.