It’s not really correct to think of the Voord as the villains of the story as they only appear briefly in episode one and then not again until episode six. Had they decided to shadow the Doctor and his friends as they quested for the keys that would added a little extra excitement, although with their wetsuits and big flippers they probably would have stood out somewhat.

Carole Ann Ford wasn’t particularly enamoured of the way Susan was portrayed in this story and it’s not hard to see why – she seems to be written down in age somewhat (acting more like a very young child at times). So given how hysterical she is in the jungle setting, it’s a blessed relief she’s packed off to the next location pretty quickly.

Things to love about this episode number one – the jungle vines that attack Susan in a less than convincing way.

Things to love about this episode number two – the statue with human arms which gives Jacqueline Hill a quick grope (although in the interests of decency it’s lucky that it could only reach her lower legs).

When they find the micro key in the first few minutes, it appears that this episode will be ending twenty minutes early. Sabetha, Altos and Susan head off for the next location whilst Ian stays behind to look for Barbara. But the key is a fake, meaning that Barbara and Ian still have to find the real one. Slimming down the cast at this point isn’t a bad move since it would have been a stretch to find something for five characters to do (even worse if the Doctor had been there as well).

And since Ian and Barbara are left alone it allows them a decent share of the action. Indeed, had it been decided at the end of The Velvet Web that Sabetha, Altos and Susan should search for the third key, whilst the Doctor went off to look for the fourth, then they could have dispensed totally with the services of Carole Ann Ford, Robin Phillips and Katherine Schofield for this episode and the production would have saved itself some money.

What Ian and Barbara find is a building full of traps. At times, all the suspension of belief you can muster is required – especially when Barbara is menaced by slowly descending spikes (of the patently rubber variety). It’s the sort of thing you might expect to see in a 1940’s Flash Gordon serial, although done somewhat better. And whilst Barbara faces death of an especially unconvincing kind, Ian is struggling to free himself from a prison of solid iron bars.

Except that they’re not solid – it looks like one sneeze would cause them to collapse. Just as it takes all of Jacqueline Hill’s professionalism to make us believe that the spikes are dangerous, so William Russell has to call on his acting experience to make the bars seem solid. Bless them both, they don’t quite succeed but it’s fun to watch them try.

All these traps have been set by Darrius (Edmund Warwick). Rather oddly he tells Ian and Barbara that only couriers sent by Arbitan would have been able to negotiate the hazards that he’s set. But Arbitan didn’t pass this information on – simple absent-mindedness maybe?

The silliest episode so far, it’s somewhat disposable fare – but at least one of the good things about this story is that we’re never too far away from a new location. And as the cliffhanger looms, Ian and Barbara find themselves menaced by some fake snow …..