No parent ever forgets that first proud procession from the car to the family home. Ali Sanders remembers every tiny detail of the day she brought her twins home - the baby seats "took up the whole of the back seat", she says.
She watched as her husband, Michael - already "head over heels in love" - clumsily fussed over the straps and buckles, like - the excited novice dad he was. Then, inside the house, came the other big family milestone - meeting the 'over-the-moon' new grandparents. 'I remember Michael's dad meeting them," says Ali, 35. "He said: "Here's Grandad!" He was so happy. Everyone was. My parents were thrilled, too."
Of course they were: this was the fairytale ending to Ali and Michael's struggle to start a family. Told they were infertile early in their marriage - with issues on both sides - the couple, from Staffordshire, threw all their efforts into the adoption process.
Just after Christmas in 2014, their prayers were answered. They were approved to adopt adorable, eight-month-old identical twin boys who even looked like Michael.
"They were chunky and squidgy, with huge brown eyes," says Ali. "Absolutely gorgeous."
The couple spent the next six weeks gradually getting to know "their" babies, visiting them at the foster home where they had been placed, decorating their nursery and preparing for the big 'take-home day'.
Life could not have been more perfect - in theory. Only something was wrong with Ali. She wasn't "getting it", she says.
Instead of bathing in a maternal glow of excitement, Ali, a school librarian, felt numb and flat.
"It felt like I was playing - that it wasn't real," she says. "What made it worse was that Michael bonded with the babies immediately. He already felt like Daddy."
She would watch him changing nappies and cooing during visits . . . but felt absolutely nothing.
She remembers taking the boys to the park for the first time in the beautiful new double buggy she had "obsessed" over for months.
"It sounds daft now, but so much effort had gone into getting the perfect buggy. It was an iCandy double and cost more than $1,931. But even when I was sitting with my beautiful buggy containing these gorgeous babies, I just wanted the process to stop. I'd never felt so lonely in my life."
Motherhood often feels overwhelming and adoptive parents are not spared the waves of panic. There is even a condition called 'post-adoptive depression'.
But this was something else.
"My overriding memory is of sitting there praying that the twins wouldn't wake up, because when they did, I'd have to go back to pretending to be a mother again," Ali recalls.
Seeing her obvious misery and panic, her husband begged her to go to the doctor only a day after they brought the twins home. He knew something was wrong. She had felt "out of sorts" for weeks.
The GP asked for a urine sample, left the room and returned with astonishing news: Ali was pregnant. She was dumbstruck.
"I said: "I just can't be" and he asked: "Why?" I said: "Because we are infertile and we've just adopted baby twins."
Legally, of course, they hadn't. The adoption process takes months to finalise through the courts. But, as far as everyone involved was concerned, they were already Mum and Dad.
The couple drove home in stunned silence, then Ali sent her husband out to buy another pregnancy test - "the most expensive one he could find, I was convinced the GP had got it wrong". But he hadn't.
Shocked, Ali and Michael called their social workers. And that was that. By the end of the day, the adoption process was off.
"I told the social worker I didn't think we would be able to keep the twins," says Ali, tearfully.
The babies went back to their foster parents that very evening.
"It was the last time I saw them. I cried and cried. I hadn't expressed any emotion until then, but when they were taken from my arms for the last time, something inside me broke and I don't think it will ever be fixed again," she says.
"I don't think the guilt will ever go. I let down these babies who had already been let down."
Some will never be able to fathom how a woman so far into the adoption process could backtrack - "they will think: How evil," Ali concedes. Others, though, will sympathise with a woman who, in impossible circumstances, made a terribly difficult decision that she considered best for everyone.
Now, with the benefit of hindsight, Ali thinks that from the moment she was pregnant the adoption was doomed, because her body simply refused to allow her to bond with babies that were not genetically hers.
"I think it was a physical thing. The way I couldn't connect with the twins was completely out of character. I'd always been really maternal and desperately wanted those babies.
"I think it was my body saying: "Concentrate on your baby." I put my biological baby first and will have to live with that for the rest of my life."
Four years on, and that baby is now a three-year-old whirlwind called Jacob. And Ali is expecting again - another pregnancy that has defied the odds - her baby girl is due in October.
She and Michael couldn't be happier. Yet, neither has been able to forget the baby boys who were so nearly theirs.
Ali rises to get two hanging toys from the sideboard. They are gingerbread men, Christmas decorations purchased when they received the news that they had been matched with the twins: "We put them on the tree that Christmas, thinking there would be a lifetime of decorating the tree."
These are the only mementos of the twins left in this house. As soon as the adoption process was halted, the couple were asked to erase all correspondence and photos of the twins, who have since been adopted (happily, it seems) by another couple.
Memories are harder to wipe, though. Ali has written a book about her difficult journey to motherhood - one that took her through not only a failed adoption, but also severe depression. At one point, she says she even contemplated suicide.
Quite understandably, she is concerned that she will be judged. "I would hate people to think I was like a child, handing back a toy when I didn't want it any more. What we did broke my heart."
Ali had always wanted to be a mother. From a happy family herself, her earliest recollections are of playing with dolls.
When she married her university sweetheart, Michael, in 2012, they were keen to start a family.
After trying for a year with no luck, they went for tests. The results were distressing.
The chances of them conceiving naturally were "impossible", says Ali. "Tests revealed I wasn't ovulating. Even when I went on Clomid [a fertility drug], the fertile phase of my cycle wasn't long enough to result in a pregnancy."
Meanwhile, tests on Michael revealed issues with sperm count and motility.
Devastated, the couple immediately ruled out invasive fertility treatments such as IVF and went straight down the adoption route. "I'd seen friends go through fertility treatment unsuccessfully," says Ali. "I'd also never been hung up on having a child that was biologically mine. To me, it didn't matter. If there were children out there who needed a loving home, we could provide it."
They went through an extensive vetting process, which included assessments, interviews and home inspections - friends and family were interviewed, too.
While some couples wait for years to be paired with a baby, Ali and Michael received a call just a few weeks after their approval, telling them they were being considered to adopt not one baby, but two.
They were given information about why the babies had ended up in care, which Ali cannot share. She admits that parts of the official report "made us both weep".
The twins had been born prematurely, and while there were no major health issues, there were developmental delays and they would need more care than most babies of their age.It is now obvious that during her very first meeting with the babies, at the foster carer's house, Ali was suffering morning sickness.
"The first time I saw them they were lying on the floor. Michael went straight to them. The room was reeling, and I didn't. I look back and think: "That was not me. The old me would have been down on the floor without a doubt."
That early introduction was supposed to be joyful, but Ali felt an odd detachment 'as if watching someone else. I held them, of course. I could coo over them and see how lovely they were, but I couldn't feel it.'
She put her unease down to the feeling of being "watched" by the foster carer and social workers.
Over the next month, there were regular visits, each longer than the last, culminating in the couple looking after the twins for a whole day. Michael took the lead in doing all the feeds and changes. Ali says she "chipped in", but had to force herself to engage.
"I was feeling so sick. All I wanted to do was lie down."
Was Michael concerned? "Yes. He knew I wasn't myself," Ali says. "But he also thought that it was just the stress of the situation. We both thought it would settle down when we got them home."
The day before they were due to collect the twins for good, they had an argument.
"Michael couldn't understand. He said: "This is what you have always wanted - why aren't you more excited?" That made it worse, because I didn't know why."
When Michael forced her to go to the doctor, she only gave in "so I could get away from the babies for a while". Michael went, too, and burst into tears as news of the pregnancy was broken. "Happy tears," she clarifies. "But we were both reeling."
They drove home in silence and then told Ali's mother and sister, who had been babysitting the twins.
"Everyone was stunned. No one knew what to say," says Ali.
Eventually, Michael said: 'We have to talk about this. Do you want to go through with the adoption or do we need to reconsider?'
One might imagine that such a momentous decision would be taken over days, if not weeks. Yet, once Ali had confessed that she didn't think she could deal with a double adoption and a pregnancy, the die was cast. "We had no idea they would take the twins that night, but they said it was for the best."
The goodbyes were upsetting for all involved. Ali wept, as did everyone in the room. "As the social workers took them from us, I knew I did love them, but I also knew this was the right thing, for them and for us,' she says.
That night, she could not stay in the house, so went to her mum's, while Michael packed up all the baby equipment.
"I couldn't look at it," she says. "We passed everything on to the foster carers because it was only right the twins should have them."
Ali has questioned her decision many times, perhaps unfairly. She says the social workers themselves told her that if she and Michael had not given up the twins, they may well have been taken back into care anyway. "They said they would never have been placed in a home with other children, because babies who are up for adoption need such specialist care."
She still had to battle with the emotional fall-out. And her pregnancy with Jacob, who was born in October 2015, was far from easy. She suffered bouts of depression and, while there were "moments of pure joy", it was clearly difficult.
Even when Jacob arrived, the bonding she had hoped for was not instant. "It took time," she admits.
Ali is comforted by the fact the twins found a forever home, and she remains convinced she made the only decision possible. She and Michael don't discuss it much, though, because it is too painful.
Now, she says, every time she sees twins of that age, she wonders: "Could that be them?"
Her greatest wish is that one day the boys will come knocking on her door. She has drafted a letter which the adoption agency says can be put on their file. What does it say?
"That it wasn't their fault, that they did nothing wrong, and that I'm sorry we let them down."