Jane - Hawking's life support: A new documentary on the cosmologist reveals his gratitude to his first wife

Stephen Hawking, the world's most famous living scientist, has paid a remarkable tribute to his first wife, who is the unwitting star of a new documentary on the life on the cosmologist to be released next month.

Jane Hawking, who was involved in an acrimonious divorce from her husband in 1991 after 26 years of marriage, is given a leading part in the film, co-written by Hawking, to describe the difficulties of living with a proud and independent man who suffers a long, debilitating illness.

The film highlights the role played by Jane in saving Hawking from a deep depression when he was first diagnosed with motor neurone disease in 1963 and her refusal to allow doctors to turn off his life-support machine in 1985 after a near-lethal attack of pneumonia while on a visit to Switzerland.

Perhaps for the first time, with Hawking's tacit approval, Jane is able to explain publicly how it felt to be the woman behind the man whose brilliant mind is trapped within a paralysed body.

While bringing up three small children, Jane had to take on the onerous tasks of caring for her increasingly crippled husband who for many years had refused any outside nursing help, expecting his wife to care for him by herself.

At the same time, his global fame began to increase, especially after the publication of his bestselling book A Brief History of Time, in 1988, which went on to sell 10 million copies worldwide. "We were under scrutiny when Stephen became rich and famous. The media were in the house and camera leads were absolutely everywhere – it was just nightmarish," Jane said when her own book of their life together was republished in 2007.

"I was expected to say, 'Isn't the way we live beautiful?', 'Aren't we lucky?', 'Look how well we've coped', when that wasn't the truth at all. It was a desperate struggle to survive day to day," she said.

The strains in their relationship began to show and it culminated in separation and divorce. In 1995, Hawking married one of his nurses, Elaine Mason, whom he divorced in 2006.

In the documentary Hawking, directed by Stephen Finnigan, the cosmologist pays fulsome tribute to his first wife, saying it was his love for her – and hers for him – that brought him out of a Wagnerian depression after his initial diagnosis.

The second crucial moment of support came in 1985 when Jane refused to allow Swiss doctors to turn off her husband's life support.

Although Stephen and Jane remained angry with one another for many years, the documentary shows there has been a remarkable reconciliation.

'Hawking' premieres at the Cambridge Film Festival on 19 September and is available to own on DVD, Blu-ray and digital download from 23 September