Sesemann, who worked at Leeds General Infirmary throughout the coronavirus pandemic, celebrated his 29th birthday by competing in his first ever marathon.
Incredibly, he ran a time of two hours, 12 minutes and 58 seconds which secures qualification for the European Championships and Commonwealth Games.
Reflecting on the last couple of years on the ward, Sesemann said: “It’s been difficult for my colleagues and I have tried to support them as much as I can.
“There have been challenges but more around Covid risk for myself. I have done all this training and been trying to avoid catch Covid beforehand. It wouldn’t be worth it.”
Sesemann trains with his dog Kipchoge, named after marathon great Eliud Kipchoge.
He added: “She’s great. She has Strava and she’s on 80-plus miles a week. She will do 20-milers and stuff. She seems to love it - but she doesn’t get a choice.
“She doesn’t pace me. She usually lags behind, but she’s a stalwart on the Leeds training scene.”
The race, the first full-scale running of the event in more than two years, was won by Sisay Lemma of Ethiopa in 2:04.01.
Bizarrely Lemma was cleared to compete but was not allowed to stand on the victory podium alongside Kenyans Vincent Kipchumba and Mosinet Geremew - who came second and third respectively - due to coronavirus protocols.
The 30-year-old had tested negative but as a contact of fellow Ethiopian Kinde Atanaw, who withdrew after a positive test on Saturday, he was whisked back to his hotel as a precaution.
Instead it was left to his agent, Gianni Demadonna, to top the podium.
Meanwhile Britain’s Charlotte Purdue proved a point by becoming the third fastest British woman in history.
Purdue was angry at being overlooked for the Tokyo Olympics and sent a blunt message to selectors with a 10th-placed finish in 2:23.26.
“I did feel I deserved to be in Tokyo,” she said. “Obviously I wasn’t selected but I put all my emphasis on this race as soon as I wasn’t.
“Luckily I had this race to focus on. If I didn’t it would have been way tougher for me because I need to have a focus for my training to execute 120 miles every week.
“Do I feel vindicated? Yes, definitely. The London marathon is such a special event. It is not like a ‘B’ race. This is my Olympics. It is as special to me to run like this in London.”