Andrea Hewitt lost the 'love of her life'

Andrea Hewitt's fiance Laurent Vidal died of a suspected heart attack. Photo / Jason Dorday

Kiwi triathlon star Andrea Hewitt has lost the "love of her life" who she was going to marry after the Rio Olympics next year, her former coach says.

French Olympian Laurent Vidal, 31, died in Gigean, France of a suspected heart attack in his sleep on Tuesday night.

Hewitt, 33, was with her fiance, who was also her coach, at the time.

The double Olympian's Christchurch-based parents, John and Margaret flew to France this morning to be with her. Her sisters Tina Cox and Sara Hewitt, along with other friends and triathlon colleagues, are also on their way to support her.

Hewitt's former coach, Dr John Hellemans, described Vidal as a "wonderful guy".

"They had a lovely relationship, so for her to lose not only the love of her life but also her coach, is just a double whammy for her," he said.

Laurent Vidal "embraced the New Zealand culture". Photo / Greg Bowker

In April last year, Vidal went into cardiac arrest following a training swim at a pool in Sete in the south of France, his European summer training base.

He experienced chest pain while swimming and left the water to seek help from employees at the pool.

He was airlifted to a hospital in nearby Montpellier, where he was placed in an induced coma for at least 48 hours.

After the incident, he retired from competition and turned to coaching.

Dr Hellemans said the transition had been "very smooth".

"As far as everybody knew, things were hunky-dory, so this is totally unexpected ... really tragic."

Dr Hellemans first met Vidal at a dinner after the Beijing Olympics in 2008.

He said Vidal was "eyeing Andrea up", and he was concerned that a relationship could affect her career or become a distraction.

However, his fears were unfounded as it "worked out very well".

Vidal soon divided his time between Waimairi Beach, Christchurch and Sete.

He endeared himself to the Kiwi triathlon community and wider public by calling himself 49 per cent Kiwi and 51 per cent French.

"He was a very intelligent guy, of very cheerful nature, and he immediately embraced the New Zealand culture and the way we practice sport," said Dr Hellemans.

"We often had them over socially ... he was always very inquisitive as far as training methods was concerned, developing an interest in the principles of [New Zealand runner and athletics coach] Arthur Lydiard, so him and I had a very similar coaching philosophy and we had a lot of good discussions around that."

He said Hewitt and Vidal were "extremely close", describing their relationship which straddled professional realms as being "exceptional".

"Coaching your partner is a no-no in sport," said Dr Hellemans.

"But for them, it worked almost from the start. A lot of it was due to Andrea's personality ... she is very open and straight-forward to coach so they were able to separate their relationship from the business of doing training.

"They never had any serious arguments."

The pair got engaged earlier this year.

Dr Hellemans assumed they would get married after the Rio Olympics next year.

Triathlon New Zealand high performance director Graeme Maw said he was "absolutely devastated".

He described Vidal as a "super young man".

"He was obviously a highly accomplished athlete in his own right and forging what was going to be an exciting career in coaching," he said.

Mr Maw said he briefly spoke to Hewitt last night.

"She is understandably devastated right now," he said.

"She has very very good support around her."

Mr Maw said he would be maintaining close contact with Hewitt, who has asked for privacy for the time being.

- Additional reporting, Solbin Kang of NZME News Service