One day Llŷr Rees was running 10 miles and preparing to enter triathlon competitions - the next he was fighting for his life.

The aneurysm and resulting aortic dissection left him close to death, with doctors fearing he would not even survive the ambulance journey from Ysbyty Gwynedd, Bangor, to Liverpool’s Broadgreen Hospital, having been rushed there from his Anglesey home.

It was four year-old daughter Catrin who found him clutching his heart on the living room floor before alerting her mum, who called for paramedics.

Had they not been home, Llŷr would not be around today.

Now he is urging people to get behind North Wales NHS charity Awyr Las (Blue Sky) and the NHS Big Tea event. Which begins today (Monday) – the 73rd anniversary of the NHS - and runs throughout July.

Llŷr is also supporting their campaign to raise funds for a revolutionary mobile cardiac scanning vehicle that will allow clinicians to diagnose and perform assessments on patients like him remotely in rural communities.

“There were no warning signs, it was like a bolt from the blue; I felt something snap in my chest and then lost consciousness for several minutes.

“The day before, I had run 10 miles – I used to run 25 miles a week – and then out of nowhere I was in hospital. Fit and healthy one minute and in the blink of an eye it was looking like I was going to die.

“It’s a very serious condition, one doctor told me after surgery that the first sign of it is usually when an autopsy is conducted - I find that terrifying, it hammers home how close I was to death.”

After 10 days at Broadgreen, Llŷr returned home and began a slow and steady period of rehabilitation.

He will have to undergo biannual assessments and is returning to gentle exercise but admits the mental scarring will take longer to heal.

“The amazing children and parents at the school raised some money for me to treat myself, so I bought a bike to help with my recovery; it gives me a lift and the drive to get better and back to where I was with my fitness.

“And all of us are supporting the NHS Big Tea event on the same day as our sports day, having been generously gifted 100 cakes by our local Morrisons supermarket. I hope others will celebrate with us.”

He added: “The NHS staff who helped me were absolutely amazing, if not for their intervention I would not be here today.

“We talk about the NHS being heroes but that doesn’t do them justice, they are a step beyond that, and I will forever owe them a debt of gratitude.”

The cardiac diagnostic vehicle will be purpose-built to include a remote medical unit complete with portable scanner, a computer desk, sink and cleaning facilities and an electric adjustable bed.

Cath More, Awyr Las Support Manager, said: “Llŷr’s recovery from such a traumatic condition is inspiring and we are so grateful for his support, and that of the parents, children and staff at Ysgol Gynradd Bontnewydd.

“To be so fit and healthy one minute and then experience such a traumatic episode must have been frightening and reinforces our campaign for the cardiac diagnostic vehicle. It is so important to get checked out if you experience any symptoms at all, and to be aware of the signs.”

Over the last 10 years, Awyr Las has received more than £25m in donations. That support has helped pay for state-of-the-art equipment and new facilities, staff training, world-class research, special projects, additional services, and extra patient comforts which are over and above what NHS funding can provide.

The charity has been encouraging the public to join the NHS Big Tea in July and be part of a national outpouring of thanks while raising money for the incredible staff who have been there for the nation over the last year.

To raise funds for the Cardiac Diagnostic Vehicle and for information on the NHS Big Tea event, visit the website: www.awyrlas.org.uk/big-tea