Thirty years ago, a rally in Britain forced the medical profession to rethink how women should give birth.
On 4 April 1982 up to 6,000 people travelled from across the country to Hampstead Heath in north London to defend a woman's right to give birth in any position she chose. It was a key moment in what became known as the active birth movement.
The action was prompted by a dispute at Hampstead's Royal Free Hospital, when one woman tried to give birth on all fours. She was asked to sign a disclaimer during the final stages of labour absolving the midwives of all responsibility. In the end, she gave in and gave birth on her back.
At the time it was standard practice across the UK for women to labour and give birth lying on a hospital bed. Any other method was seriously discouraged.
"The head obstetrician at the hospital said active birth was animalistic behaviour, and that humans were not animals and should lie down to give birth," says Janet Balaskas, who organised the rally and is now seen as the founder of the active birth movement in the UK.
She had begun training as an antenatal teacher and had coached her mothers-to-be to use whichever position felt most comfortable in birth, whether that was squatting, standing or on all fours - she called it "active birth".
The thinking was that women without any obvious medical complications could give birth in as natural a way as possible without the use of drugs or anaesthetics. It didn't mean rejecting medical intervention entirely but placed a greater emphasis on the role of the woman rather than the medical profession.
But these ideas were not welcomed by some in the maternity unit - and the head obstetrician banned the practice.
"I didn't want women's labours to become a battleground for active birth," says Ms Balaskas, but she felt compelled to act as more and more women came to her complaining that they had been robbed of their right to give birth in the way they found most comfortable.
"It was almost like the need for a woman's body was becoming obsolete, once she'd carried the baby to term.
"It was like the plan was to get us into hospital, strap us into beds, pump us full of artificial hormones to get the process going, give us an epidural and if that didn't work then give us a Caesarean section."
Ms Balaskas had spent the previous year researching birth and labour after finding that many of the women she dealt with were unhappy with the way their births were managed in hospitals.
"I looked up how women gave birth in other cultures and throughout the ages. It was a revelation - there were no images of women lying on their backs."
As part of her antenatal training she was given a model of a pelvis, and after studying the textbook Gray's Anatomy realised that gravity formed an important part of the birthing process.
"As soon as you lie the mother on her back, the diameter of the pelvic outlet is reduced."
She describes it as a eureka moment: "No wonder women were struggling to give birth on their back, no wonder it was so unmanageably painful."
Pregnant with her third child, she decided to try out a new position herself and hired an independent midwife to help her give birth at home.
Her doctor, intrigued, asked if he too could attend. He had just been on holiday to Botswana and had seen a woman give birth squatting.
Her daughter was born safely and she was more keen than ever to share this experience with other mothers.
"I believed that my body was designed for giving birth and that birth could be one of the best experiences of a woman's life."
That was certainly the case with many of the women who attended the Pithiviers Hospital in France under the direction of obstetrician Michel Odent. One woman told a BBC television programme in March 1982 that birth had felt like a "love wave, or orgasm".
Dr Odent, like Ms Balaskas, was one of a handful of proponents of active birth in the West - his clinic was the first to introduce the water birth. She invited him and several other activists to speak at the rally.
'Sea of faces'
The original idea was to hold a "squat-in" in the reception area of the Royal Free Hospital. "I had a vision of a few families and relatives," she says. But soon interest in the protest grew.
"It all happened very quickly; it took just three weeks to organise. The phone kept ringing with offers of help. We even received a stage for free from a very well-known rock band."
In the end, the rally was held on Hampstead Heath close to the hospital. "I started to hear that people were coming in coachloads from all over the country."
Ms Balaskas describes feeling very excited and quite scared on the day of the rally: "I didn't imagine I'd find myself in the middle of something like this."
On stage, Dr Odent tapped Ms Balaskas on the shoulder and said: "Look behind you".
"I saw a massive column of people walking towards us... I just saw a sea of faces, posters and banners… women, babies and dads with kids on their shoulders - an amazing crowd of people who were all there because they were concerned about birth."
Thirty years on, there is now a unit at the hospital dedicated to active birth which aims to avoid medical intervention if possible, and there are similar facilities up and down the UK.
Ms Balaskas says she actually agrees with the head obstetrician who described her methods as "animalistic" back then.
"Our needs are very similar to any other mammal," she says. "We need a safe, quiet, warm place and no-one telling us what to do because our bodies know it all."