Counting World Championships and World Cup medals in his impressive tally, as well as sitting on the second position of the World ranking, Burnell, 27, has largely contributed to British marathon swimming success for the most part of the last decade.

In light of this announcement, Burnell, who has challenged the biggest names of the discipline such as Ferry Weertman (NED) in Rio 2016, said:

"It's not a decision that I've come to lightly, but it's one that, over the last year or so, has been in the wings, waiting. From a physical and mental point of view, it's definitely the best decision for me at this time.”

Everyone - my friends, my partner, my family, training partners, everyone at the National Centre - has been so supportive. I couldn't be more thankful to them for that, because that was a huge weight off my shoulders.
By Jack Burnell (GBR)

"I'd thought a lot of people would be asking, 'is this the right time?' with the Olympics around the corner. But that didn't happen.

"They know me best and they know that I swim for one reason and one reason only - and that is to be the best in the world. My body is not at a stage right now where it would let me do that.

"I felt I wanted to end my career on my terms. I just thought of sitting on the side of the road in Tokyo, having come 10th or 12th - I don't want to sign my career off in that way, having had some amazing highs in my career, being ranked second in the world, winning World Cup medals, things like that. I wanted to sign it off in my way and on my own terms."

Coming back on his incredible journey, he added:

"My career has just been an absolute rollercoaster of emotions. We've had the ups, like being ranked second in the world, World Cup medals, European medals. They are all great, and at the time, you kind of gloss over them. Usually, it's the lows that stick out to you at the time," he explained.

Funnily enough, my career highlight and my career lowlight were at the same time, in Rio. Pulling on the Team GB jersey made me feel complete as a swimmer. But then what happened in terms of the result (Jack was disqualified at the end of a race in which he was in genuine contention for a medal) was probably the lowest moment of my career. I've never just sat and stared at the floor of my hotel room longer than I did after that race, just not knowing what had gone on.
By Jack Burnell (GBR)

"But again, those moments are all part of the journey and the experience I can take from what I've done, which I can put into the next chapter of my life. Had I not experienced those things, I wouldn't be as well equipped."