Since the show was brought back, there has never been a classic series writer return to the show. There's been classic series directors - Graeme Harper - and classic series actors - Elisabeth Sladen, John Leeson, Christopher Benjamin etc.... - but never classic series writers. Until now. Finally a classic series writer has written for the new series - Rona Munro, the writer of the 1989 classic series serial Survival.

The Eaters of Light sees the Doctor (Peter Capaldi) land the TARDIS in Second Century Scotland to test Bill's (Pearl Mackie) theory about what really happened to the missing Ninth Legion of the Roman army. Meanwhile, a light-eating locust has come through a portal from another dimension, and has been feeding on the Roman army...

This episode is probably the closest to the classic series the new series will ever get. Throughout Murray Gold's music is very reminiscent of classic-style incidental scores, and the Doctor is written more in the vein of the classic incarnations of the character. Peter Capaldi plays it brilliantly, and his performance allows the different approach to feel like the same incarnation we've grown to know and love over three series. He bares more similarities to the Series 8 version of the 12th Doctor in this episode than the softer Series 9/10 12, but it makes sense for the character's more pacifist tendencies. The brutality doesn't feel particularly random, the Doctor is simply fed up of the rivalry between two warring factions (Romans and Pictish warriors). It's a return to the theme of 'If we fight like animals, we die like animals!' from Survival.

One improvement the classic series approach has over the new series style is that the guest characters feel more fleshed out. We get to know these characters more; their personalities and what makes them tick. The new series generally tends to treat them as merely functions to the plot, whereas the classic series taught you to care for them as much as you do the TARDIS crew. Here they feel more like people rather than objects for the writer to play with. A particular standout is Lucius (Brian Vernel), a compassionate bisexual Roman soldier who befriends Bill.

Some viewers have taken issue with the past being shown as diverse in both this episode and Thin Ice, but personally I don't see the issue. It sends out a nice message of inclusivity to viewers who are black and/or with a differing sexuality to those of us who are straight. It's the right kind of message Doctor Who should be sending: the Doctor should be teaching the audience that it doesn't matter if you're black, white, blue, straight, gay, bisexual, have one head or no head it's who you are inside that counts. If that means showing a more ideal version of history, then so be it.

There's another and far more interesting choice that this episode makes than a bisexual Roman however. Many new series episodes tend to feature a lot of their monsters; The Eaters of Light, on the other hand, fits into that new series rarity where you rarely see the creature in full. The episode is more like Closing Time, for example, than it is The Impossible Astronaut/Day of the Moon. For most of the story we only see glimpses of the creature, and this is a wise choice because much like Jaws when you see the creature in full its very unconvincing. The CGI appearance of the light-eating locust is poor, and it appears much more threatening when its lurking in the shadows. Once it is revealed you can tell it's not really there; it looks hideously fake, and takes all tension out of the episode.

The episode is also let down by being way too talky. There's too many conversations going on in this story, and it slows the plot down to a stand-still. A lot of the scenes are expository, with Rona Munro deciding to 'tell not show' rather than the more enjoyable 'show not tell'. This episode achieved the lowest AI of the series so far, and it's not surprising. The Eaters of Light is an episode that could have benefitted from stricter script editing to cut out the unnecessary padding and replace it with scenes that strive to show the audience something instead.

Then there are certain occurrences that take place that make the episode feel like it should have aired much earlier in the run. Bill falls down a hole...again, after falling down a hole in the previous episode Empress of Mars too. Nardole (Matt Lucas) nags the Doctor about guarding the vault...despite Missy being in the TARDIS at the end of the previous episode...yet Nardole is surprised to find her there when they return to the TARDIS. Bill doesn't know about the TARDIS translation circuit...despite having been travelling with the Doctor for quite a few adventures since the first episode. It feels as though this episode was originally episode four of the run, and these continuity errors make the story feel out of place. It's a shame more attention wasn't given to the show's continuity, as this is the kind of thing us fans notice.

The final scene between the Doctor and Missy (Michelle Gomez) is nice, if a little too long. Rona Munro clearly understands these characters and their shared history, and whilst it's obvious Missy is playing the Doctor it will be interesting to see what will happen tonight when the Doctor tests whether she is really turning 'good'. There will inevitably be consequences, and I wouldn't be surprised if it is revealed that Missy has been tampering with the TARDIS.

Overall, The Eaters of Light is a dull episode. The guest characters are stronger than usual, and it's interesting to see a classic series style adopted for a new series episode. Unfortunately the episode is let down by too many talky scenes, and the CGI is ropey. There are various plot inconsistencies too that leave the episode feeling out of place in episode ten of the twelve episode run. There's a nice scene between the Doctor and Missy however, which demonstrates how much Rona Munro understands the dynamic between the two characters.