Master documentary maker Louis Theroux has recently been filming with struggling mums at a psychiatric hospital in Bromley.

The BBC documentary, Mother’s On The Edge, will be broadcast on Sunday and follows four mothers at Bethlem Royal Hospital who have developed mental illness since giving birth.

Louis learns what lies behind the mother’s struggle and speaks to staff on the mother and baby unit about how they care for vulnerable parents.

Dr Gertrude Seneviratne, of South London and Maudsley NHS Trust which runs the hospital, thanked the women and their families for contributing to the documentary.

He added: "Their contribution helps to shed light on these important issues and reduce stigma around perinatal mental health.

"The arrival of a baby should be the happiest time in a woman’s life, but for some women this is not the case - our research shows that one in four women experience mental health problems during pregnancy or shortly after the baby is born."

Deborah Griffin, clinical service lead on the mother and baby unit, said the film crew was present during some "very challenging times".

She added: "The documentary is sensitively made and gives a rare, compassionate but enquiring insight into the world of perinatal mental health, the complexity of the difficulties that the women admitted to us are experiencing and highlights the impact of social media on the pressure women experience to be the perfect mother when they are struggling to manage.

"It also gives a message of hope, as we see our mums get better and return home with their babies."

Mothers on the ward are supported by psychiatrists, psychologists, mental health nurses, nursery nurses, midwives and other professionals.

Louis Theroux: Mothers On The Edge will broadcast on May 12 on BBC Two at 9pm.