Mark Gatiss has been waiting his entire life to write upcoming Doctor Who episode ‘Empress of Mars’.

This Saturday’s instalment brings back the Martian species known as the Ice Warriors, a classic series monster originally revived for a submarine-set adventure by Gatiss in 2013’s ‘Cold War’.

This time, it’s a Victorian expedition party who awaken a hibernating fleet of Ice Warriors and their Ice Empress despite warnings from The Doctor (Peter Capaldi).

Gatiss chatted about the return of the Warriors of Mars on The One Show on Wednesday (June 7), revealing that this particular storyline is one he’s long dreamed of making a reality.

“Steven Moffat’s leaving. Peter Capaldi’s suddenly leaving,” he explained. “I just said to Steven, ‘Can I do the story I’ve always wanted to do?’ He said, ‘Yeah, go on!'”

The writer also opened up about his creative process, and specifically how he conceived of this meeting of Victorian adventurers with one of Doctor Who‘s oldest monsters.

“You have to think about how [the story] is going to be achieved,” he acknowledged. “One of the great things about Doctor Who always is that the setting will always tend to be an isolated group of humans under threat.

“I’ve [thought of] the Ice Warriors on Mars, which I’ve always wanted to do, but it’s a whole civilisation. It’s a sort of isolated Victorian expedition [this time] in a tomb. You’ve got to think about how it’s going to be achieved.”

‘Empress of Mars’ may turn out to be Gatiss’s final-ever Doctor Who story, as this marks the last series for long-time showrunner and Mark’s personal friend Steven Moffat.

Earlier this week, Gatiss put anxious fans at ease in an interview with Digital Spy when he teased that he’s already working on a new project with Moffat. (It’s not more Sherlock though!)

Doctor Who airs ‘Empress of Mars’ at 7.15pm on BBC One, and BBC America airs the show in the US. Watch a trailer for ‘Empress of Mars’ below: