There's one thing I find strange about Planet of the Spiders. The 1974 Doctor Who serial was the regeneration story of the much beloved third Doctor (played by Jon Pertwee), yet for some reason it is very rarely discussed among the Whovian fandom. It almost seems to have been abandoned by the fanbase; even Invasion of the Dinosaurs is talked about more than this serial. In my opinion, this serial definitely doesn't deserve to be forgotten.

Planet of the Spiders is arguably Doctor Who's first example of a series finale. It sees a number of elements from Jon Pertwee's time on the show resolved including the Metebilis 3 crystal and Mike Yates' (Richard Franklyn) betrayal, so not only is the story frequently ignored but it has arguably had a major influence over the new series and the way everything is resolved in a finale.

In Planet of the Spiders, the mutated giant spiders known as the 'Eight Legs' are seeking the Doctor's Metebilis 3 crystal in order to achieve universal domination. The Doctor is the only one who can stop them; he must confront the Eight Legs' leader The Great One and face the possible death of his current incarnation in order to save the day.

One of the things that made Jon Pertwee's era so brilliant was the concept of threats close to home as the villains. It is therefore genius that for his last adventure, the villains are something we recognise from our own planet that many find frightening: I am of course talking about spiders. This serial is wise in its decision to follow in the steps of The Green Death (featuring giant maggots) and The Mutants (giant insects), both highly regarded among Whovians.

It wouldn't feel right for Jon Pertwee's last serial if the story's antagonists weren't similar earth-like creatures, although it is a shame that Roger Degaldo's Master couldn't have featured in his last story as originally planned- sadly Roger Degaldo died in a car crash in 1973. The Eight Legs may not be the most convincing Doctor Who prop but the classic series isn't about the special effects anyway, it's about the narrative and having an adventure with the Doctor. And there was never a more exciting adventure during Jon Pertwee's era than when he tackled monsters close to home.

The decision to include a chase sequence with the Whomobile and Bessie is also to be applauded. These two vehicles are synonymous with the third Doctor era of the show and it is nice that they got the send-off they deserved along with this incarnation of the Doctor. Bessie in particular is a car you can't imagine with any other incarnation and a big part of this era. The chase sequence represents everything people like about Jon Pertwee's Doctor; he is essentially Doctor Bond during an era of television where there were a lot of spy dramas and undercover cop shows. It helps that the scene is wonderfully executed by director Barry Letts; it's one of those scenes in the classic series where arguably you cannot tell the show was working on a shoestring budget.

It's nice to see Mike Yates redeemed by alerting the Doctor and Sarah (Elisabeth Sladen) to the strange goings-on at the Buddhist meditation centre. It feels natural and in-character for Mike Yates to want to redeem himself and it's nice to see a signature UNIT personnel who was a big part of this incarnation's time on Earth become firmly on the side of good again after betraying UNIT in Invasion of the Dinosaurs. Mike feels as much like a Doctor Who companion as Liz, Jo or Sarah and perhaps one day Adam Mitchell will get a similar redemption story (although I would love to see Adam as an antagonist at some point akin to the role he plays in the comic series Prisoners of Time).

Despite the serial's forgotten nature, its ending is arguably one of the most iconic regeneration sequences in the show's history. It deserves to be. The third Doctor's regeneration is bittersweet and heart-wrenching without the need for Murray Gold music or a sobbing David Tennant.

The emotion is dealt with in a subtle way and whilst I personally love the tenth Doctor's regeneration scene, I can also appreciate how this sequence is not quite so 'in your face' about how you're supposed to feel. All this sequence needs is four simple words - 'A tear, Sarah Jane?' - and it immediately sells the emotional weight of the scene. A lot of it is down to Jon Pertwee's stunning delivery but it wouldn't have worked without Elisabeth Sladen as Sarah Jane Smith, who if you didn't know Sarah Jane was a character you'd think genuinely believed in real life that Jon Pertwee was going to die. Of course, he doesn't die - he regenerates into Tom Baker - but Sarah doesn't know that and Elisabeth Sladenplays it brilliantly.

Overall, Planet of the Spiders is a brilliant and sadly often-overlooked Jon Pertwee serial, especially for Jon Pertwee's regeneration story. The story encompasses everything that made the Pertwee era of the show special, from the Earth-like appearance of the monsters (an approach later taken to the new series by Russell T Davies) to the vehicles that quickly became synonymous with Jon Pertwee's portrayal: namely Bessie and the Whomobile. The decision to have Mike Yates redeemed in the story is a good one and the story contains one of the show's best regeneration scenes that shows you can provide raw emotion without Vale Decem and David Tennant crying on cue.