A father of three who has been diagnosed with motor neurone disease (MND) has completed his Guinness World Record attempt.

Mark O’Brien, 54, who grew up in Croxley Green, swam 11km in open water on Saturday, September 23, to raise money for the Motor Neurone Disease Association.

The lifelong Watford FC fan swam in the lake at Denham Waterski Club, with the support of his three children and 81-year-old mother.

The goal for the swim was to beat the Guinness World Record for the longest unaided open swim for a person living with MND.

Watford Observer: Mark's children, Lauren, David and Georgia supporting their dad.Mark's children, Lauren, David and Georgia supporting their dad. (Image: Mark O'Brien)

Mark said: “I am so proud of what I have achieved, it was a lot tougher than what I thought it was going to be, but it has given me a huge sense of pride and relief.

“The cold was unbelievable, and I ended up with mild hypothermia at the end but I completed the swim and had so much support from start to finish.”

The 54-year-old was joined by his three children, who he is “incredibly close to”, for the final 1.5km and he was “so proud” to be joined in the water by them.

Watford Observer: The family swimming the final 1.5km together. The family swimming the final 1.5km together. (Image: Mark O'Brien)

Mark was diagnosed with MND in March last year but left it until May of this year to tell his family as he “didn’t want this diagnosis to stop them from doing what they love”.

He was concerned that he “wouldn’t be well enough” for the challenge as in May and June of this year he was very unwell.

Watford Observer: Both Mark and his son are huge Watford FC fans. Both Mark and his son are huge Watford FC fans. (Image: Mark O'Brien)

You can donate to Mark's cause here.

Despite his son David, 21, living in Cardiff for university, the pair attend Watford games together.

Mark added: “I have always been close with all three of my children and I just want to make sure they know how proud I am of them and how much it means to me that they swam the last kilometre with me.”

Watford Observer:

He was supported on the side of the lake by his family, friends and strangers who came along to watch, and the “mood brightened” the more he swam.

He blacked out a couple times, as he found the swim “tougher than expected”, but his family knew he “wouldn’t give up” on his challenge.

MND currently has no cure, but Mark is seeing “every day as a good day”.

It can take up to 12 weeks to find out if Guinness World Record attempts have been successful.