One of the Doctor's deadliest foes has returned after hiding in plain sight on the show since Christmas 2023.

In The Church on Ruby Road, viewers met Ruby Sunday's (played by Millie Gibson) neighbour Mrs Flood (Anita Dobson).

At first, she seemed like a regular neighbour. But very quickly, the show started leaving us with questions. Like why does she seem to know what a TARDIS is? Why is she also Belinda's (Varada Sethu) neighbour? And why does she keep turning up wherever the Doctor's (Ncuti Gatwa) adventures take him.

In episode The Interstellar Song Contest (streaming on BBC iPlayer now), viewers finally learned the truth when the character bi-generated (as the Doctor had before her) and was revealed to be an old foe of the Doctor, the Rani (Archie Panjabi).

As the episode revealed, Mrs Flood is now "a Rani", while Panjabi plays "the Rani – the definite article", the newest addition of this iconic character.

Read on to learn everything you need to know about the return of the Doctor's latest adversary, as well as your guide to the episodes you should watch before the next installment of Doctor Who.

For many series of the show, the Doctor's greatest Time Lord adversary was the Master. But then during Colin Baker's run, a new foe emerged.

"She's an old Doctor Who villain who's never been brought back since the show came back in 2005," says Doctor Who showrunner Russell T Davies in a behind the scenes video, "she's been waiting in the wings and the time has come."

It was Sylvester McCoy's Seventh Doctor, who summed up the Rani perfectly. "Don't underestimate her," he said in the episode Time and the Rani. "She's a brilliant but sterile mind. There's not one spark of decency in her."

In The Mark of the Rani, starring Sixth Doctor (Colin Baker) and available as part of iPlayer's collection of classic Doctor Who, the Rani (Kate O'Mara) is introduced as a renegade Time Lord from the Doctor's home planet of Gallifrey.

Her main interest is science, but she is willing to hurt and kill for her research.

In an interview with the BBC, actor Kate O'Mara described the character as someone who attended university with the Doctor, "studying science. And then it went completely to her head, and she wanted to govern the whole universe."

In The Mark of the Rani, we learn about her time on the planet Miasimia Goria. Her experiments have taken away the planet's inhabitants' ability to sleep, causing chaos on the planet.

To reverse this, the Rani heads to 19th-century Earth, where her plan is to harvest the chemical that promotes sleep in human brains. Naturally, the Doctor and Peri (Nicola Bryant) prevent her from doing that.

When the Rani returned, it was to face off against McCoy's Doctor in his first episode, Time and the Rani.

In this serial, the Rani has brought geniuses from across time and space to the planet Lakertya, where she is forcing them to calculate how to turn the planet into a device that would allow her to manipulate evolution across the universe.

Of course, the Doctor stops her, and she is taken prisoner by the residents of the planet. How she escaped that, as well as the devastation of Gallifrey, is yet to be revealed.

In these two episodes, the Rani was played by actor Kate O'Mara, a legend of 1980s TV after playing Joan Collins' sister in the American soap Dynasty.

So it is fitting that the character is now being played by another legendary soap actor – Anita Dobson, part of the original EastEnders cast in 1985.

Archie Panjabi, meanwhile, has soap experience too, starring in The Bill and Holby City as a young actor. Her defining role, however, was in The Good Wife, which led to her being the first Asian actor to win a Primetime Emmy for acting.

To find out what these actors will bring to the role, however, and to find out what devious plans they have to challenge the Doctor, tune in to the two-part series finale, which starts on Saturday 24 May on BBC One and iPlayer.