Michelle Keegan may be leaving Our Girl – but has the next lead actress already been introduced?

Before we say goodbye to Georgie, there are four more instalments left to air which look set to concentrate on her struggle with PTSD.

But alongside that, the show may already be paving the way for the next main role – with the introduction of new medic Mimi Saunders (Amy-Leigh Hickman). Could she be Our Girl's next leading lady?

Mimi is no wallflower and has already made an impact with her impressive debut. The character displays all the qualities that have made both leads so compelling: heart, strength and determination - and a tendency to test the rules!

When a show has a central character, replacing them is never an easy task and there is always a risk that viewers will lose interest. There have already been a few notable differences this year; Captain James, played by Ben Aldridge for three seasons, has not returned and there are more new recruits including former teacher "Prof" (Nico Mirallegro). But Our Girl has survived some major changes in its time, and it can survive this too.

After original star Lacey Turner (Molly Dawes) left following an enthralling first series, her successor Michelle Keegan quickly won viewers over with equally powerful performances. She has been at the forefront of the BBC drama ever since, keeping us gripped with the more experienced Georgie’s confidence and compassion. Her love story with Elvis (Luke Pasqualino) came to an abrupt end when he was killed by a bomb during series three, much to the devastation of fans.

Before the start of this series, Michelle spoke about her love of the show - and its future. "I’m a massive fan." she said. "I was a fan before I was even in this – so I’m going to continue to watch it, definitely!"

And discussing new cast members like Mimi, she teased: "I think the audience is just going to love them, honestly, I think they’re just going to take to them really well."

She has been proven right. Amy-Leigh Hickman is winning high praise in the role, and Mimi is already popular with viewers. Like Molly and Georgie, she is outspoken and spirited - shown when a doctor informed her that the young girl she saved now faced losing a leg. "If the Queen was lying here, we’d find a way to repair her wouldn’t we?" she insisted without missing a beat.

There are reminders of series one’s fledgling medic in particular. We have watched Mimi struggle with her own nerves and self-doubt; before springing into action and showing what she is made of. And when she found herself distracted from her duties by the injured child’s uncertain future, it began to mirror the risky bond between Molly and young Afghan girl Bashira.

Despite the similarities, though, Mimi is not a carbon copy. Her own cheeky brand of personality shines through, and it seems that there is plenty to explore with her background. With an obvious reluctance to call her family and focus being given on how she is coping in Afghanistan, there is potential to tell a story with this new addition that goes beyond the job.

If the show does intend to make her the next leading lady, bringing her in with time to spare before Michelle bows out is a smart move. It’s the perfect time to introduce a prominent character, giving the audience time to warm to her and offering something else to hold their attention as they await Georgie’s fate.

There has been a constant link throughout the show’s run, as Georgie was a friend of Molly and Captain James when she arrived. It would keep the connection going if her replacement was the soldier she trained herself. What could be more fitting than that?

Our Girl has always been led by a female medic, and it makes sense for someone that has already settled in to take over. While there has been no confirmation of who is next in line, Private Saunders is certainly being taken in the right direction; making her the ideal candidate.

Our Girl continues on Tuesdays at 9pm on BBC One. Check out what else is on with our TV Guide.