It's fair to say that many were feeling apprehensive about Smile. The writer Frank Cottrell Boyce's previous work for Doctor Who - In The Forest Of The Night - was arguably the most controversial episode since Love & Monsters. I, on the other hand, was vastly looking forward to Smile. In The Forest Of The Night was one of my favourite episodes of Series 8, and I couldn't wait to see what Frank Cottrell Boyce would write next.

Robots known as the Vardy have been helping to prepare the planet Gliese 581d - a planet that bizarrely enough actually exists in real life - for human colonisation, working with their computer interfaces the Emojibots and a small skeleton crew. The Doctor (Peter Capaldi) and Bill Potts (Pearl Mackie) arrive on the colony world to find the skeleton crew have been murdered by the Emojibots and turned into fertiliser for the planet's crops. Investigating the deaths, they discover that not only do the Emojibots communicate in emoji but that these robots also kill anyone who displays an emotion other than happiness.

Strangely for a 21st century episode of Doctor Who, this episode often feels more like a classic series serial than a forty-five minute new series story. The slow pace may be off-putting to younger viewers, but for this reviewer it was a welcome breath of fresh air. I love fast-paced episodes but every once in a while it's nice to get an episode like The Rings of Akhaten or Deep Breath that gives the audience a breather from non-stop action. Those are the nearest new series parallels, but this story's pacing bears much stronger similarities to 1975's The Ark In Space. Just like that classic Tom Baker serial, Smile takes its time to explore the world of the narrative and is more focused on the Doctor-companion relationship as opposed to the episode's monster.

With any other Doctor/companion pairing, I'm not entirely sure Smile would have worked as an episode of the new series. The Doctor and Bill however are such a strong double act that you don't notice the slower-than-usual pace; every time they are on screen together, they are captivating to watch. Peter Capaldi and Pearl Mackie have a lot of chemistry together, and are exactly the kind of pair the show needs right now during its tenth series on air. Handled by a bad actor Bill's questions could easily become annoying, but Pearl Mackie makes them endearing and often they are the kind of questions you're surprised no companion has asked before. Why is the chair in the TARDIS nowhere near the controls? Why is the police box exterior signage written in English? Why does The Doctor go back to help after successfully escaping from the episode's monsters, instead of leaving in the TARDIS?

That's not to say the episode would be rubbish without Peter Capaldi and Pearl Mackie. Far from it. Frank Cottrell Boyce's writing is fantastic, often very lyrical and poetic. He makes any line of dialogue sound like it was written by a famous poet, and the show is lucky to have such a skilled writer working for the show. It's also clear from this episode's classic series similarities that Frank Cottrell Boyce knows his Doctor Who; sometimes that is detrimental to the story, as the inspiration the episode owes to The Happiness Patrol is very clear in its central premise and sometimes hard to ignore, but for the most part it feels more like a love letter to Classic Who rather than a direct copy.

One thing the classic series wouldn't have had is the rich production values of this episode. Smile was filmed in the City of Arts and Science Museum in Valencia (Spain) and the choice of filming location is so strong, it makes Doctor Who look higher budget than it actually is. The Emojibots are generally a very good design too, if perhaps a little too small for them to be seen as a dangerous threat to The Doctor and Bill.

Speaking of the Emojibots, it's a very believable idea that emojis survive as a universal language. What many viewers may not realise is that this aspect of the plot was based on actual research the writer conducted on what our language may look like in the distant future, and it makes a lot of sense given the past use of hieroglyphs by the Egyptians.

Unfortunately, Smile is let down considerably by its solution. The conclusion of the episode involves the Doctor turning the Emojibots off and on again, literally resetting them like a computer, and it leaves you wondering why The Doctor didn't just do that in the first place. It's certainly less drastic than his first suggestion - to blow the entire utopian compound up - and would have saved both Doctor and companion a lot of time. Not to mention all the lives that would have been lost if The Doctor had actually blown the place up.

Overall, Smile is another solid episode of Doctor Who and bares surprising similarities to the classic series of the show. The pace is more reminiscent of The Ark In Space as opposed to the episode's nearest new series equivalent in The Rings of Akhaten, with a stronger focus on world-building as opposed to the monster-of-the-week. After the first episode of Series 10 'The Pilot', Smile is another episode where the Doctor/companion relationship is the main focus over the monsters featured, and the pairing of The Doctor and Bill manages to hide the slow pace that may otherwise be a turn-off for younger viewers of the show. Disappointingly however the episode has a very weak resolution and Nardole barely features. Matt Lucas' Series 10 involvement so far feels more like a last minute addition to the cast rather than a natural inclusion