Start the clock. 

Experimentation is the heart of Doctor Who, but the lungs or some other important organ would have to be the ideas.

This is a traditional formula made fresh and exciting with audacity and confidence. It knows it's ideas are excellent and lets the insanity of what it's doing distract from it's technical efficiency. You aren't thinking this isn't going to actually be good, you're distracted by the pulp, the presentation. The show knows exactly what it is doing here though, and this is a plain showcase for Capaldi and Coleman at the top of their game.

Feels like the kind of episode that would benefit from a Target Novelization, but I'm obsessed with what we have anyway.

I love the 1920s-inspired setting of this story, transported into space, it is a wonderful visual. The entire events of the episode unfolding on a train, with a limited number of people aboard, draws brilliantly from Murder on the Orient Express and space travel adds a distinctly sci-fi twist.

Frank Skinner is an excellent addition to the guest cast, and the Mummy is one of the most frightening creatures ever seen in Doctor Who. It’s a huge success, both in terms of its design and the visceral tension it generates.

I could have done with about half as much of the tension between Clara and the Doctor. Capaldi’s Doctor is already dark and complex enough without creating needless barriers to his likability.

That said, this is undoubtedly a strong debut story from Jamie Mathieson. Memorable, innovative, and iconic. Even if the ending wraps up a bit too conveniently, the story’s overall quality and distinctiveness more than make up for it.

I know it sounds crazy, but this is my comfort episode of Doctor Who. I could watch it a billion times and it would never get old.

It distilled everything I love about Doctor Who: first off it's an awesome genre mash-up between history, classic literature, and sci-fi. It's a dark, dramatic story with Peter Capaldi at his acerbic best. The relationship between him and Clara is taken almost to its limit. The denouement is heart-pounding and thrilling, and there are twists throughout.

If somebody asks me what I love about Doctor Who, I'd show them Mummy on the Orient Express.

Best ep of the show so far imo. Everything I love about DW is here.

That was terrific. Never expected it to be that good, it had everything I want from Who.

Loved the way the mystery was solved bit by bit, the sets and costumes were great, the mummy was very creepy and it followed up last week's events very well too.

Pleased we're getting another Mathieson episode next week now.