A father of three diagnosed with motor neurone disease (MND) wants to raise awareness of the illness by breaking a Guinness World record.

Mark O’Brien, 54, who grew up in Croxley Green, Rickmansworth, was diagnosed with the terminal illness on March 17, 2022.

MND is a rare condition that affects the brain and nerves and causes weakness over time. There is currently no cure.

Watford Observer: Mark at the back with his children Georgia, Lauren and David.Mark at the back with his children Georgia, Lauren and David. (Image: Mark O'Brien)

In a bid to make a positive out of the negative Mark decided to take on the challenge to swim the distance of 10.5km (10,500 metres) at the lake in Denham Waterski Club.

According to the Guinness World Records, this would be the longest unaided open water swim for a person living with MND.

He said: “This is against doctors’ advice, but there are five reasons which for me override that.”

The financial travel industry investor consultant wants to highlight to others with the disease, sometimes called ALS, that “even the impossible can be possible”.

Watford Observer: Mark wants to do the swim to raise money for MND research. Right: Mark and his son David are Watford FC fans.Mark wants to do the swim to raise money for MND research. Right: Mark and his son David are Watford FC fans. (Image: Mark O'Brien)

He said: “I have had so many other families contact me to say they are inspired.”

Two other reasons include, raising awareness of MND and money for the Motor Neurone Disease Association.

He added: “I’m really close with my children, not that they need any more lessons, but one major life lesson I want to leave is to never give up. They know their dad is not going to curl up and go down without a fight.”

Finally, Mark, who has been told he has anywhere between two to five years left, wants to “use whatever time I have left in my life in the most positive way I can”.

Watford Observer: Mark and his children on a family holiday.Mark and his children on a family holiday. (Image: Mark O'Brien)

The life-long Watford FC fan, who now lives in Slip End, Bedfordshire, is a keen sportsman who has done several charity swims in the past and decided this route was a good way to raise money and awareness.

It will be held on Sunday, September 24, starting at 8am and finishing around four to five hours later.

He said: “For people who live with MND, one of the only places they feel relatively normal is in the water.

“Sometimes I struggle to walk down the road and can be completely wiped out and have to have sofa days, but then I can bash out five or six kilometres in the lake.”

But the challenge does not come without its struggles. Having started training for it every day, he recently had to go down to twice a week.

Watford Observer: Mark's children will be swimming the final laps with him.Mark's children will be swimming the final laps with him. (Image: Mark O'Brien)

When he takes on the record, he will have health professionals and his swimming coach Alex Walker on site, and oxygen to assist him when he needs it.

He will also be joined by his children Lauren 24, and twins David and Georgia, 21, for the final stages.

Of his diagnosis, he said: “At first, I was in a complete tailspin. I am pretty strong mentally, but this sent me sideways, I was in denial, and it was mentally crushing.

“But the challenge has given me something to focus on. My objective is to stay alive long enough for a cure.”

So far, he has raised £4,300 of his £25,000 target.

He said: “The first donation came from a woman who I haven’t seen since primary school.

“The donations are not just about the money, but also the sentiment and the thought.”