A private nightmare made public

Alyssa is 25 days old. Her life is hanging by a thread. She has a hole 30cm in circumference in her skull where her sister Bethany used to be. Shaun and Mary Nolan, the twins' parents, are already grieving the death of Bethany. Now Mary is by Alyssa's side in intensive care and Shaun is driving home to be with the family's three young sons. We take a detour to a river on the north side of Brisbane, Australia, where the family lives. It is dusk, and while we're talking Shaun's mobile rings. "Yes... yes... yes." I guess it is Mary on the other end. "Yes... yes... Love you, too." They hang up. Shaun says: "It's good news. Scott Campbell says she's going to pull through." Scott Campbell is the neurosurgeon who carried out the operation to separate Alyssa and Bethany 72 hours earlier. Shaun smiles, lifts his can of beer to the sunset and then begins to cry: "We might have a few problems with her, but who cares? She's going to live. Finally, some bloody good news. Finally.

Alyssa is 25 days old. Her life is hanging by a thread. She has a hole 30cm in circumference in her skull where her sister Bethany used to be. Shaun and Mary Nolan, the twins' parents, are already grieving the death of Bethany. Now Mary is by Alyssa's side in intensive care and Shaun is driving home to be with the family's three young sons. We take a detour to a river on the north side of Brisbane, Australia, where the family lives. It is dusk, and while we're talking Shaun's mobile rings. "Yes... yes... yes." I guess it is Mary on the other end. "Yes... yes... Love you, too." They hang up. Shaun says: "It's good news. Scott Campbell says she's going to pull through." Scott Campbell is the neurosurgeon who carried out the operation to separate Alyssa and Bethany 72 hours earlier. Shaun smiles, lifts his can of beer to the sunset and then begins to cry: "We might have a few problems with her, but who cares? She's going to live. Finally, some bloody good news. Finally. I just want to bring my daughter home."

The next week, Shaun and Mary were burying Bethany. It is difficult to exaggerate the emotional demands that had been placed on Shaun and Mary over the previous eight months. In the space of a few weeks they had learnt that, unexpectedly, Mary was pregnant; that she was having twins; and then that the twins were joined at the head. Surprise. Delight. Horror. More than that, one daughter had just a single kidney; the other had no bladder and no kidneys at all. It was always going to be difficult.

Two questions need to be asked: why did Shaun and Mary go ahead with the pregnancy? And why did they allow cameras to follow them on their journey?

The first is perhaps the easier of the two to answer. Shaun and Mary have the same religious background. Both were brought up in Catholic families, Shaun rather more seriously than Mary. As a young man, he might have gone into the Church, and by the time Scott Campbell began the operation to separate Bethany and Alyssa, Shaun was carrying his rosary and warning God of the consequences if He let them down. Their sons attend the local Catholic school, and in the weeks before the birth, they had their house blessed by the local Catholic priest.

But Shaun and Mary are not regular churchgoers. They lived together, and their two eldest sons, Ryan and Jayden, were born before they had decided to get married. So there was nothing preordained about the decisions that they had to take.

Shaun once remarked of the option to terminate the pregnancy: "I don't think I had it in me." Mary was less absolutist, more morally pragmatic. What was an essentially moral decision was a question of balancing conflicting demands. Fortunately for their relationship, the result was the same. They continued with the pregnancy.

This was how Mary put it: "We went through a lot of heartbreak. We had to decide what was best for the twins, and for us as a couple, and what was best for our three sons as well. We thought: if we decide to continue [with the pregnancy], is that selfish, because the boys are going to find it hard? But then again, if we don't continue, then we haven't given them a chance. We agreed quite early that if they weren't going to have any quality of life, it wasn't fair to bring them into the world."

On the basis of sparse medical statistics, doctors at the Royal Brisbane Hospital put the chances of both girls surviving the birth and an operation to separate them at no more than 33 per cent. For some while, they expected Shaun and Mary to go for termination. Then the decision was made.

"I'm not particularly religious," said Mary, "but I remember saying to Shaun one night: 'We're being asked to play God here. How do you decide whether someone lives or dies?' Then a couple of nights later, I said to him: 'We don't have to. It's not up to us to decide. If it looks like they are going to have some sort of decent life, who are we to take it away from them?' If we terminated, we hadn't given them a shot."

So Mary went ahead with the pregnancy, hoping that doctors might find, in each scan, Bethany's missing kidneys, or that the join was smaller than had been predicted. Nothing changed.

This was the film we were trying to make. An ordinary couple, faced with an impossible moral dilemma, takes a decision that has utterly unpredictable consequences. They are committed to living with the outcome whatever happens. It was going to be as much about Shaun and Mary as their daughters.

But how to explain their decision to go ahead with the documentary? The strains on the family were obvious. Shaun and Mary knew that there would be difficult, perhaps tragic, times ahead. Why make it more stressful by inviting strangers into your home to record not only what you do but also, with a lot of emotion around, how you feel?

Partly, it was the advice they were given. A year earlier, Scott Campbell separated another set of conjoined twins at the same hospital in Brisbane. They, too, were joined at the head, though less severely than Bethany and Alyssa. When the news broke, the hospital used a public-relations company to handle the media. It seemed to work.

From the start, Shaun and Mary were pointed in the same direction. The PR company advised them to strike a deal for an exclusive documentary that would allow the rest of the media to be kept at arms length. The result was a co-production between Granada Television in the UK and Channel 9 in Sydney. And again, it worked. The pregnancy didn't become public until the final days. The Australian media, perhaps surprisingly given the parentage of some of Britain's tabloids, behaved impeccably. In return for the odd press conference with Shaun and medical staff, the family was left alone.

In part, of course, Shaun and Mary's decision to approve the filming would give their daughters a degree of financial security. This must also have been a part of their calculations. The television companies made a payment into a trust fund to be used to help bring up Bethany and Alyssa, both of whom, joined or apart, would have special needs.

Even so, Shaun and Mary could have said no, but they went ahead. Then something happened. Shaun was always more vulnerable than his wife. Where Mary became focused and resilient, to outsiders appearing to shut down the emotional in favour of the practical, Shaun was shredded by the trauma of the pregnancy. For him, participating in the documentary, and the people with whom it brought him into contact, became a sanity-saving diversion. Here he found amateur therapists, friends and drinking partners that just about kept him on the tracks. The result was honest and heartbreaking, raw and, sometimes, almost unbearable.

And perhaps there we have another reason why Shaun and Mary agreed to the documentary. They were just a regular couple from the "modest" northern suburbs, doing what they thought was right: taking a difficult decision, and living with the consequences. Here, perhaps, was something that might just encourage and sustain others.

It was hard enough for the rest of us. They asked me to do a short reading at Bethany's funeral about not forgetting, as if one could or would. To paraphrase Louis Theroux, I arrived a television producer and left as a friend. It is not always like that.

Shaun and Mary believe everything happens for a reason. If it does, it's not always clear what it is. So nearly a year on, they have a sister for their sons, but are still struggling for answers.

"Maybe the reason for the girls was to teach us to be more appreciative of what we have got," Mary said. "Maybe the reason for the girls was to let other people know how important simple things are. Maybe the reason for the girls was to bring all of us together as a family. Any one of these things could be the reason. Or maybe it will reveal itself later."

'Joined at Birth', produced by Andy Webb, is on Channel 4 on Monday 8 April at 9pm