Hollywood actor Alistair Petrie has told for the first time of the harrowing moment doctors warned one of his prematurely born twins might die.

Alistair and Lucy were delighted in 2002 when they discovered they were finally having twins after Lucy suffered three miscarriages and an ectopic pregnancy from which she almost died herself.

But 30 weeks and two days into the pregnancy Lucy suffered stomach pains and was rushed into hospital where 36-hours later she gave birth to two tiny premature baby boys.

While little 4lb Brodie quickly gained strength and was able to breath on his own, his brother Cal, who tipped the scales at just 3lb 2oz and was born 90 seconds earlier, was struggling to breathe unaided.

After spending 48 hours in intensive care unit he was then moved to a high dependency unit but his condition failed to improve.

It was at that point, as Lucy cared for Brodie in a hospital bed nearby that Alistair was forced to ask whether Cal might not make it.

He was told that if Cal had developed interstitial pulmonary lung disease, as was suspected, the most horrific scenario was a distinct possibility.

WATCH: Alistair Petrie gets emotional talking about his twin sons

Yorkshireman Petrie, who has appeared in Rogue One: A Star Wars Story and The Night Manager, agreed to be filmed with wife Lucy to mark World Prematurity Day (November 17) and show support for the Borne charity.

Father of three Alistair, 47, said: ‘’The consultant said, ‘Yes. It’s possible he may die’.

‘’Instead of falling apart, I instinctively knew I needed to be clear headed, I needed to somehow take charge of this situation and be resolute for my wife and my new born son.

‘’No one else could be cast in this role. It had to be me. So you do it. A hidden part of your character somewhere inside you is called upon.

‘’You step up because there is no choice. I had to ask the question: ‘Will my son die?’

‘’Because I needed to know all eventualities, all possible outcomes.

‘’To prepare, to be ready - and to avoid the reality was to somehow to do a disservice to this small human I had helped bring into this world. It wasn’t his choice, it was ours.

‘’I owed him absolute honesty. My job was to protect him. And to protect Lucy from asking the ultimate question.’’

Cal was eventually moved to Brompton hospital and was due to undergo an operation to have his lung tissue tested for the rare condition.

But miraculously he developed the ability to breathe on his own just hours before surgeons were due to open him up, and he was allowed home two days later.

The couple married in Windlesham, Surrey three years after they met and three years later Norfolk-born Lucy fell pregnant with their first child Angus, who was born in June 2000.

As the middle child and with plenty of cousins in the background too Lucy, 51, yearned for a big family so the couple kept their fingers crossed Angus would soon have a little brother or sister to keep him company.

After the miscarriages Lucy and Alistair feared they would never have more children.

So when Lucy did a home pregnancy test in September 2002, the couple treated the news with caution and went for an early, five-week scan.

As the nurse carried out the ultrasound she announced there were two heartbeats.

After Alistair asked if one was Lucy’s, the couple were told: ‘’No, there are two foetal heartbeats.’’

Alistair said: ‘’When we got outside it was about a five minute walk to the car, but we must have walked around for about 40 minutes trying to take in what we had been told.

‘’I was just laughing. I couldn’t believe it. After everything we had been through we were going to be having twins.’’

In March when the pregnancy reached the 30-week mark – doctors had told them getting to 28 weeks dramatically increased their chances of both babies born healthily - Alistair and Lucy finally allowed themselves to celebrate.

The couple travelled from their home in south London to Mothercare in Kew where they stocked up on all the essentials, including a top of the range double buggy.

The following day Lucy felt pains in the right side of her stomach as the couple sat at home watching a friend star in a TV drama.

Lucy initially dismissed her discomfort as wind and it was only when Alistair laid down the law that she agreed to go for a check up.

Shortly after arriving at King’s Hospital in Herne Hill, London where she was due to give birth it was decided she needed to be moved to a hospital where two incubators were available.

So Lucy was transferred to the Chelsea and Westminster hospital where she underwent an emergency C-section. The premature boys arrived and were taken into the ICU.

Alistair said: ‘’I was ecstatic. I always assumed one would be a girl. I thought I would be a father to a girl.

‘’I looked at Lucy and said ‘We’ve got three boys!’’

‘’I felt empowered and ever so proud of Lucy. The boys were both obviously premature but in good nick, they had hands, fingers and feet, everything was in place.’’

Brodie went from strength to strength but little Cal’s oxygen requirements were fluctuating, prompting doctors to put him on an oxygen substitute.

Admitting they were puzzled by the irregular rates of his breathing the medical team contacted Canadian lung disease experts who suggested he may be suffering from interstitial pulmonary lung disease.

Alistair was advised of the potentially life-threatening issue and warned if Cal did pull through he may have to carry an oxygen tank around with him for six to eight years.

The decision was made to move Cal to Brompton hospital in early May and operate to test the lung tissue for disease.

But as the surgeon checked his breathing before the op by lowering the oxygen levels gradually he discovered Cal was able to breathe by himself.

For a decade he was an out-patient, undergoing regular checks, but now aged 14 and a keen trampolinist, Cal is able to lead a full and healthy lifestyle.

Alistair said: ‘’We know how lucky we are. There were some dark moments.

‘’During those moments Lucy and I worked as a team, we always have done.

‘’We absolutely came together, and we came through it all. I knew my role was to as emotionally strong as I could be.

‘’I’m good in a crisis – But Lucy is one of the toughest people I know. She’s extraordinary in that regard, she is emotionally resolute.

‘’I know situations like this would break some couples, but we came together. I can say I am a father of three amazing boys. And I am incredibly proud to say that.’’

Alistair and Lucy became involved with the Borne charity through a friend of theirs actress Natascha McElhone, who had two boys delivered by Professor Mark Johnson and has become a long-standing ambassador for the charity.

In 2007 the Pertries swam the English Channel together to raise money for the neo natal unit at the Chelsea and Westminster hospital and raised £25,000.

Johnson, who set up the charity in 2013, is the Clinical Chair in Obstetrics at Imperial College and Professor of Obstetrics at the Chelsea and Westminster Hospital where he is focused on high risk maternity care.

With dual expertise in obstetrics and research, he is in a unique position to tackle the problem of preterm birth.

Premature babies face many challenging issues from the moment they are born.

For those that survive, many are faced with a lifetime of disability from cerebral palsy, autism, deafness, blindness to development delays and learning difficulties. Medical research provides the foundations for lasting change.

Prof. Johnson said: “Only by changing the beginning can we change the outcome for millions of unborn children, and give them the chance of a full life unaffected by disability,”

To learn more about the campaign use the hashtags #WorldPrematurityDay and #BorneWonderland2017 or to donate go to the Borne website.

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