What's Wrong With... Earthshock

The cave with the bomb seems to be in the middle of nowhere, so what geographical relation has it to the forthcoming conference?

Why place the device somewhere accessible, where it might be found and deactivated? Why not simply stick it in a hole in the ground and bury it, or drop it in the ocean?

If it's a planet-destroying bomb, it could have been placed thousands of miles away where there would be less likelihood of security searches.

The conference surely includes lots of different aliens, so why do the troopers have a scanner that can only pick up mammalian lifeforms? It's a conference to establish an alliance against Cybermen, so shouldn't they at least be able to pick them up on their equipment?

What if an enemy wanted to use robots? Oh look - they have used robots.

The sentinels actually draw attention to the bomb, sort of defeating the whole subterfuge thing.

The Cybermen assume that their plans are fool-proof, but surely they understand the concept of "contingency". They are relying entirely on a single bomb, which has already been disturbed by cavers, so why didn't they think of having a second, or even third, device elsewhere.

The fact that they have placed sentinels shows that they expect potential tampering.

After all, in Revenge of the Cybermen they knew that one bomb would be enough to destroy Voga, but still had three of them carried into the heart of the asteroid.

They are also quick enough at coming up with a 'Plan B' when the bomb is deactivated. Why not have 'Plan B' in place from the start?

Radio signals travel at 186,410 miles per second in space - so why does it take a whole minute for the Cyber-signal to get from the freighter to the bomb? Just how far out is this vessel?

Why did the Cybermen kill some of the crew if they wanted to keep a low profile of the freighter? They can't all have stumbled into their secret lair.

Scott is a member of Earth's security forces - so why did the Doctor not call on him the minute he and Adric were captured. Why leave him in the TARDIS in the first place?

The Doctor is a suspected murderer, yet Briggs allows him and Adric to remain on the bridge, unsecured. She and Berger simply go about their business with their backs to the pair of potential killers.

It isn't made very clear why the Cyber-Leader leaves a significant number of his troops on the crashing freighter - nor why they suddenly activate remotely. Where do they go to? Only a single damaged Cyberman makes it to the bridge to stop Adric's meddling.

How do the first lot of Cybermen get off the ship? The Leader takes to the TARDIS, but where does his army go? How many escape pods does this sparsely-crewed freighter need? It is logical that the crew might try to escape, so why leave them a pod anyway?

Why did the Cybermen capture Tegan, when they've been killing everyone else? Why, in general, do monsters always seem to know which members of the cast are the regulars?

This one generated heated debate in the pages of DWM: how can the Cybermen have footage from Revenge of the Cybermen when it takes place far in their future? How can they have footage from The Tenth Planet when not only did every Cyberman perish, but so did their entire planet? Uploaded to some computer archive just doesn't wash.

Stuff everyone notices:

One of the troopers turns to look back, and fails to spot the obvious moving shadow of an android on the cavern wall, despite staring right at it.

A couple of Cybermen seem to be having a very casual chat in one scene.

A member of the production team can be seen lurking under a stairway, as spotted by Peter Davison when watching the DVD with the contrast turned up.

A female trooper is grabbed by a Cybermen just as she is about to walk into the TARDIS, yet is seen entering unharmed seconds later.

You can see David Banks' battery pack sliding down his chin, before the clear chin piece suddenly becomes opaque - and earlier his voice modulator picks up Davison's voice briefly.

Earth didn't look like it does today 65,000,000 years ago - and wouldn't have been in the same location in space back then for the freighter to crash into it.

Adric miraculously intuits that the console is about to explode several seconds before it happens. Mr Waterhouse rather spoils the moment.

And can anyone really take seriously the idea of Beryl Reid as a tough space captain?