Sunetra Sarker tells Gabrielle Fagan why she really left Casualty, and explains why marriage isn't top of her agenda right now.

After nearly nine years playing the often reckless Dr Zoe Hanna in Casualty, Sunetra Sarker finally decided to follow in her character's footsteps and "take my own risks for once, and stop playing it safe".

The actress shocked fans of the BBC medical drama by suddenly leaving the series in May, and for the first time she explains what led to her departure, how she's coping with life after Casualty, and why she won't marry "the love of my life".

"I honestly never thought I'd leave Casualty, and I really miss Zoe. It's been sad, emotional, but really exciting as well, and I'm glad I made the decision to go," declares the 43-year-old, as she chats at the Bristol home she shares with her partner, businessman Scott Carey, and her 11-year-old son Noah from her marriage which ended five years ago.

Her character's been one of the best loved on the Saturday evening show and has had several high-profile storylines, including an affair with a married man, infertility and the adoption of the daughter of a dead friend.

"Zoe had so many sides to her - a dedicated doctor, a sassy single mother and someone who was also vulnerable, flawed and an emotional car crash - let's not forget her series of disastrous affairs! Constantly trying to understand her and work out what made her tick has made her fascinating to play," says Liverpool-born Sunetra, who first found fame as Nisha in Channel Four's Brookside in the late 1980s, and has also starred in Cold Feet, Emmerdale and Holby City.

Sarker credits her on-screen character with helping her find the courage to make her own dramatic career move.

"Zoe's made me a stronger person because playing her has allowed me to look at life in different ways. She was a risk taker and always embracing challenges, and partly because of her, I'm no longer so set in my ways.

"I'm also more confident about voicing my opinions, because she's helped give me a 'voice'. I'm more forthright. You get used to thinking, 'I can stand up for myself', when you constantly portray a woman who does just that all the time," she says.

It emerges though that, despite her clear affection for the medic, she'd secretly been wrestling with abandoning her for two years - since she turned 40.

"That birthday was a bit of a reawakening for me. I was at an age when I felt like I'd ticked a lot of things off my list - a good career, being a mum, a lovely home - and it felt nice and stable, but a bit of a plateau," she says.

"I thought, 'You're supposed to be a fully-fledged grown-up now, so this is the time to be brave, and if you're going to try new things, you need to get on with it!'"

Taking part in Strictly Come Dancing in 2014 - she was eliminated ninth - was the first step she took to test her appetite for change, but the experience didn't have the effect she expected.

"Strictly was fantastic fun and I made friends for life of the other girls on the show, but it's so scary at times - the pace is punishing, with full-on training and no time for anything else. Taking part resulted in further delaying my departure from Casualty," she admits with a smile.

"Afterwards, I couldn't wait to get back to my 'day job' doctoring and being safe in the arms of a series I totally loved and not on something where I could get booted off!

"But something in my head still kept nagging, 'It's now or never if you're going to make a change', although it took me until this year to finally say, 'That's it, I need to go.' Fortunately, the producers were brilliant about my decision to leave; they've said the door's always open for Zoe to return [the character's left to work in America], so I wasn't heartbroken feeling I'd never wear the stethoscope again!"

Since then, Sarker's career has gone from strength to strength. Early next year she'll be on screen in two ITV crime dramas, Broadchurch and Safe House, and she also has a guest part in BBC's Death In Paradise.

Sarker, an ambassador for charity, Sightsavers, which works to restore sight and prevent blindness in the world's poorest countries, will also discover that she has illustrious ancestors in India in BBC's Who Do You Think You Are series.

While she's looking for new work experiences, she has no desire to change her blissfully happy personal life, which is in complete contrast to the turbulent Dr Hanna's.

She and her partner, Scott, who has two children, 12 and 15, have been together five years, but she vows she's not looking for marriage.

"Scott and I were friends all through college and met again by chance after we were both divorced. It was like a thunderbolt for us both at that reunion and we had such a connection, we knew we'd be together forever," she says.

"We're like soppy teenagers who leave each other surprise love notes and have such a harmonious relationship - we both feel equally lucky to have found each other.

"I feel married, but, although I have a yearning to call Scott my husband, I don't want a wedding just to prove to other people how happy we are. Also, part of me worries it might jinx or ruin things in some way and make us take our relationship for granted.

"I honestly never imagined being as content emotionally as I am today, and all the decisions I've made since I was 40 have led to me now being at my most peaceful and fulfilled."

:: Sunetra Sarker is an ambassador for the UK-based charity Sightsavers, which works to restore sight and prevent blindness in the world's poorest countries. A sight-restoring operation costs Sightsavers just £30. Visit www.sightsavers.org