A "pioneering" scheme in Sheffield has helped boost children's sleep by 2.4 hours a night, NHS England says. How does a sleep clinic look to improve the lives of families?
"They were waking up anything from 10 to 40 times a night - and that's no exaggeration," says Jacqui Wolstenholme, remembering her restless nights trying to nurse her twin daughters, Jessica and Jasmine, back to sleep.
The now four-year-olds have always had difficulty sleeping but the evenings and nights became something to dread.
"At around three months old, when a lot of babies start to settle, things were just getting worse, and worse, and worse. They hardly ever slept," Jacqui tells BBC Two's Victoria Derbyshire programme.
"I would have one in bed with me and the other one would be with Julian [their father] in another bedroom. He was trying to settle one, I was trying to settle the other."
It began to take its toll on both parents, who themselves became sleep-deprived.
Jacqui had planned to return to her job in graphic design after 12 months - but it became clear there was "absolutely no way" this could happen.
"My husband was having trouble holding down his job," she says, "just through sheer exhaustion."
The Wolstenholmes are far from alone.
Prof Heather Elphick says the UK is "in the midst of a hidden public health crisis when it comes to sleep".
"There are more children who can't sleep than we realise and I think it's something parents are not happy to talk about," she says.
"They feel that people are judging their parenting skills if their child can't sleep, so don't go and find help."
Prof Elphick helped launch a pilot scheme involving 40 families at Sheffield Children's Hospital's sleep clinic - in combination with NHS England and the local council - aimed at improving children's sleep patterns.
It has now been extended across the city, helping 800 children a year.
Jacqui's daughters had similar treatment - though their conditions are more severe.
At the clinic, the process begins with a long, detailed medical history - going right back to the birth - as well as a look at the child's sleeping environment.
For the twins, this was an important factor in understanding where the issues may derive.
"They've suffered with chronic recurrent illnesses and repeated hospital admissions," Jacqui says, "so their first few years have been pretty tough."
Nurses at the sleep clinic helped the family develop a strict bedtime routine for the girls.
"The hour before bed, we dim the lights downstairs. The TV, radio and screens go off - and we do colouring, drawing, building games, anything that involves hand-eye coordination," Jacqui says.
"Then, they go upstairs for a bath and straight into the bedroom.
"We stick to exactly the same routine - even down to the same wording we use when we say goodnight to them every night. It's about consistency."
According to NHS England, the scheme in Sheffield has led to children gaining an extra 2.4 hours sleep per night and the time taken to fall asleep dropping from over two hours to just over 30 minutes.
Parents and carers have also reported their quality of life has improved, it says, including them having a better relationship with their child.
Sleep problems can be a particular problem for children with disorders such as attention deficit hyperactivity disorder (ADHD), those who have been adopted, and those that have experienced neglect or trauma.
Jenny Lowis and her "very energetic, boisterous" son, Noah, have also had issues around bedtime.
In the middle of the night, she says, he "would bang the door so I would wake up and if that didn't work he'd come to the side of my bed and just scream".
"You would literally get up [in the morning] and think, 'I don't even know what time it is, I don't know what day it is, I don't know where I am,'" Jenny says.
Noah, too, had health issues at a young age.
"When he was born, he had quite bad colic, so he was being sick at night," Jenny says. "The nights were just so long, so, so long."
Noah now also has a new bedtime routine and, as part of the programme, has undergone a sleep study - where he was monitored by doctors.
He was diagnosed with parasomnia - a disruptive sleep disorder that can lead to night terrors, sleepwalking and sleep talking. For Noah, it means he "talks, shouts, screams, cries and laughs during his sleep".
Jenny says it was of huge comfort to know there was a medical reason behind his sleeplessness.
They are still getting help from the clinic but things are improving.
"When things were really bad, he couldn't hold his focus on a single activity for longer than five minutes," she says. "Now, he's actually starting to sleep in his own bed and his concentration is a lot better in school."
Jacqui's twins have been given the all-clear from the clinic.
"I don't even like talking about the days prior to sleep," she says.
"It's still not something that comes naturally to them - we have to stick to routine - but on a good night we can walk out [of their bedroom] and then 12 hours later they will wake up."