Richard Curtis has revealed his sister committed suicide following a 25-year battle with psychological illness, as he said society was “failing” to focus properly on mental health.

The screenwriter behind Love Actually and Notting Hill said his sister took her own life the day before a planned party for her, adding he believed his family “couldn’t have done anything more right”.

The relative is believed to be Belinda Curtis, one of the screenwriter’s two older sisters, who died in Sydney around the time of her 55th birthday in 2009.

“We had a 25-year stab at trying to help my sister and couldn’t do it,” Curtis told an audience of doctors.

The co-founder of Comic Relief, which has raised millions for mental health causes, described suicide as a “psychological heart attack – just a series of events that lead you somewhere they might not have done”.

Speaking publicly about the tragedy for the first time, the 61-year-old director said: "I so don't believe in thinking about what you could have done.

“I can't talk about it, I get too emotional.

“But the circumstances of my sister's suicide could not have been jollier as it were.

“They had shopped for her birthday party the next day, couldn't have done anything more right, and yet that was still the day she chose to take her own life.

“I don't think it's in our hands."

The Blackadder mastermind was praised by the Samaritans and other mental health campaigners for helping shine a light on the reality of suicide.

In 2010, Curtis wrote the screenplay for an episode of Dr Who, which addressed the subject through the character of Vincent Van Gough.

This week he told a gathering at the Public Health England annual conference he believed attitudes were beginning to improve.

"Sometimes you realise the thing you’ve been working for has got far enough to actually start spreading with extra speed," he said.

“We’ve been working on mental health issues and I suddenly feel again, particularly with this young generation, is that they understand that mental illness isn’t the same as physical illness, but is as complicated.

“I think it will be one of the huge things in the next 10 years.”

His daughter Scarlett has previously spoken of her struggle with depression and anxiety in the aftermath of a debilitating physical illness in her teens.

Sue Baker, the director of Time to Change, a charity funded by Comic Relief, said: "It is helpful for the public to realise how common mental health problems are and they can affect any of us, regardless of circumstances.

"Having high profile people talk about their own mental health does help people shift their thinking towards the one in four of us who do have problems."