Former professional cyclist will walker now works to raise the profile of heart disease prevention. Source: News Corp Australia

He hasn’t been on a bike since because his heart might not stand the strain.

And since that dramatic day in Buninyong, near Ballarat, he has almost died several more times, including a horrific experience recently when the temperamental ticker tried to shut down nine times in 40 minutes.

It was “the deepest, darkest place I have ever been — you couldn’t be any closer to death”. For an immensely talented young athlete who was told by an international expert he had the “motor” to be as good as Cadel Evans, life has taken a dangerous turn.

But at least Walker is alive — even if he sleeps with the lights on because he is terrified he might not wake up.

William Walker hasn’t been back on a bike since his illness nearly killed him. Source: News Limited

Walker, 28, is now devoting his time to helping lower the death toll from heart disease in men, which runs at 40,000 a year.

“It hurts a bit,” he said of the lost chance at sporting glory. “But I have enough years left to do something so significant that it doesn’t hurt you not being a cycling champion. I know it’s a cliche, but I want to make a difference.”

Walker has accepted a job at the Baker IDI Heart and Diabetes Institute, an international medical research facility in Melbourne.

He is using his network in cycling and other sports to raise the profile of heart disease prevention, much in the way that breast and prostate cancer fighters have been able to do through sporting identities such as Olympic athlete Raelene Boyle and the late Robert Flower, the AFL star who died of heart disease at 59.

Walker has a combination of arrhythmia, which involves an irregular beat, and tachycardia, which makes the heart beat faster than normal but pumps less blood around the body. It has twice destroyed a cycling career that could have been anything.

Will Walker was a rising star in world cycling. Source: News Limited

At 19, he won the Australian championship and a silver medal at the under-23 world championships. His potential was so obvious the big Dutch pro team Rabobank snapped him up, giving him rides in the Italian Giro and the Spanish Vuelta grand tours.

The world was at his feet and the biggest race of all, the Tour de France, was only a matter of time.

Doctors suspect lightly built Walker might have taken on too much too soon with the two three-week races. When his form mysteriously declined his heart condition was diagnosed.

No fewer than five operations followed, the last in 2010, with no guarantee of a full recovery, although there was no suggestion that his life was in peril. With little option but to retire, he spent time working with GreenEDGE, which made him realise he was miss competition.

He convinced doctors to approve a comeback which looked on track when he unleashed a highly impressive ride to finish a close second in a stage of the 2013 Herald Sun Tour, riding for prominent local team Drapac.

Walker’s career ended as a result of a combination of heart conditions. Source: News Limited

“I needed to try cycling again. I wasn’t ready to give it up. I was watching these guys and thinking, ‘That was me’. I had this burning desire,” he said at the time.

“But I’m healthy now and feeling good about being back on this side of the fence.”

The feeling lasted 12 months.

In Buninyong, by now riding for a team from Azerbaijan, he was among 17 riders who broke away from the peloton and was feeling good to go on with it.

But on the mountain that defines the championship course, his bike computer showed his heart was racing at 270 beats a minute, three or four times faster than normal.

He thought he was having a heart attack and would die on the spot. By the time an ambulance got to him, he had so little blood going to his brain he could not think or talk coherently and relied on onlookers to tell paramedics what had happened.

Walker looked set for a long and successful cycling career. Source: News Limited

Soon after, he had another operation to insert a defibrillator, a device that monitors the heartbeat and if it cannot control it within eight seconds of it becoming irregular, he is hit with a massive and very unpleasant shock.

“Without it, I would have been dead several times this year,” he said.

The most recent near-disaster happened at home as he was setting out for a stroll.

The defibrillator hit with full force. He swallowed every pill he had and got his brother to rush him to hospital, where the tiny machine went off eight more times.

Asked whether he fears for the future, Walker said: “I have a lot of anxiety, especially going to bed. There are a few sleepless nights, sleeping with the lights on. I try to read until as late as possible so I fall asleep from exhaustion.”

Walker holds a degree in finance but has become so knowledgeable about and fascinated by the heart that he has ambitions of becoming a medico himself.

Meanwhile, his priority is to highlight the need for men — and women — to get tested regularly, live healthily and eat properly.

“Right now, I feel pretty good. My heart rate is perfect and it looks positive for the future,” he said.

Smiling wryly, he adds: “But I’ve said that before.”