The fourth segment of the Key to Time is upon us...but where will the search for the Key to Time take us now?

Well, until the land of The Prisoner of Zenda it seems. Sorry, I mean 'The Androids of Tara'. The serial was written by David Fisher as Doctor Who's take on 1961's popular U.S. adaptation of the adventure book The Prisoner of Zenda. It's basically the equivalent of if the new series of Doctor Who decided to make a pastiche of Game of Thrones. The new series has taken influences from popular forms of media (Last Christmas is clearly inspired by Alien) but they appear more as forms of inspiration rather than direct copies.

Now I'm not sure how much The Androids of Tara's plot copies that of The Prisoner of Zenda as I have neither read the book or seen the U.S. drama. I am not a fan however when writers make a conscious decision to mimic the plot of something else as David Fisher and producer Graham Williams decided to here. Whilst it is true that all ideas have been done at some point and no idea is truly original, it seems unimaginative to make that decision to use another writer's plot.

The plot sees the Doctor (Tom Baker) and Romana (Mary Tamm) arrive on the planet Tara; at first, their trip seems rather straightforward when Romana finds the segment of the Key to Time straight away. When she is attacked by a Taran Wood Beast, Count Grendel of Gracht (Peter Jeffrey) comes to her rescue and takes her into his castle. However it turns out that he thinks he's one of her androids: an android replica of Princess Strella, who looks exactly like Romana. Grendel has taken Tara's next in line to be king Prince Reynart (Neville Jason) captive and plans to marry Strella so he will be crowned at Reynart's coronation in his absence

Whilst I do not approve of the intentions to copy The Prisoner of Zenda, on its own merit The Androids of Tara is a lot of fun and certainly better than The Stones of Blood. The sword fight between the Doctor and Grendel is brilliantly staged by director Michael Hayes and looks like something out of a movie rather than a TV Show. The android doubles and not knowing who is or isn't an android is well-executed too, especially with the added complication that Romana looks exactly like Android Strella and real Strella.

Speaking of Romana, Mary Tamm does an excellent job of playing essentially three different characters - android, Strella and Romana. She manages to make each feel distinct and yet also similar enough to cause confusion over their same appearance. Mary Tamm's portrayal of three different roles really shows her capability and skills as a Doctor Who companion actor. It's a shame she has since passed so cannot return to the show but luckily Mary Tamm managed to record some Big Finish audios before her passing. It would have been sad if the average Key to Time season had been her last in the role.

The Androids of Tara also has some of the classic series' best location work. The use of Leeds Castle works well for this story as it has a nice medieval feel that adds to the visual aesthetic of Tara whilst also providing a nice contrast with the futuristic android technology. More importantly: it feels like a setting from an adventure story and fits the fairytale-esque tale of knights, damsels in distress and sword-fights the story is trying to tell. It looks like particularly expensive location work too; nothing in the serial looks cheap, which is impressive given the shoestring budget.

Overall, The Androids of Tara is not the most imaginative serial - it was thought up as 'Doctor Who does The Prisoner of Zenda' - but it is a lot of fun to watch. There's a brilliant sword fight between the Doctor and Grendel and the android doubles adds a nice complication to the plot. Mary Tamm is outstanding at playing three different characters in the android Strella, the real Strella and Romana, giving them enough differences to feel like separate characters yet also maintaining certain similarities so you're not entirely sure who is who. There's some great location work too; the Leeds Castle location makes for an effective medieval adventure setting and allows for a nice contrast between the old fairytale and the advanced android technology in the serial. Just don't expect anything original.