Point 783 sees a Gerry Anderson series use one of Doctor Who's tried and tested scenarios, that of the base under siege, with a runaway Unitron kicking up a storm out in the desert.

After the Mysterons threaten to kill the Supreme Commander of Earth Forces, Captains Scarlet and Blue are assigned to protect him. They thwart one attempt on his life when a Mysteronised Major Brookes blows himself up at a conference. But danger threatens again at remote military base Point 783 when a prototype tank, the Unitron, is being demonstrated. The vehicle is programmed to attack the building where the Supreme Commander is watching and it's up to Captain Scarlet to save the day.

Series like Scarlet and its predecessors feature a multitude of vehicles in order to avoid the puppet characters having to walk so it's more by luck than design that the format lends itself to commenting on the advances in mechanisation and automation of the 1960s. This episode introduces the Unitron, an unmanned tank which can be computer controlled to automatically attack a designated target. As with your Crabloggers, Pacific-Atlantic monorails and Sidewinders, the keywords here are 'fully automated' and 'virtually unstoppable'. Once it's realised that the Unitron is locked on computer control, the only option is to blast it before it blasts us. A neat thumbs-down for compete automation, I'd say (just like the Star Trek episode The Ultimate Computer and the Secret Service episode Recall to Service) - it's a theme revisited in one of the writers' other episodes, Seek and Destroy, where the Mysterons take control of three Angel aircraft and aim them at their originators. Whether the writers see the remote Point 783 as a metaphor for a Britain under threat from all this automation, as has been the case many times in Doctor Who, is of course open to the viewer's interpretation. But it's worth considering that a good writer will weave a message of his own into the action, children's fiction or not. After all, Grimm's fairy tales and Aesop's fables can be interpreted on several levels, so why not a TV series?

The story also stresses the very alien nature of the Mysterons with both of their agents willing to commit suicide for their cause, a throwback to the Kamikaze pilots of WW2, a period through which many of Century 21's staff would have lived, as well as tactics employed by all-too-real 21st century terrorism.

The episode is quite a bloodthirsty installment, with a head-on car crash showing mangled bodies lying in the wreckage, plus an exploding Mysteron agent. Undoubtedly this level of carnage would not have been permitted in a kids TV show if it had been filmed in live-action, yet the fact that they are puppets allowed Century 21 to go into much darker territory than previously. The writers, Peter Curran and David Williams may have been influenced by the opening episode as their segment also features a car crash and two separate attempts on the victim's life. As with Special Assignment, the Mysterons' methods are a tad convoluted - it appears they've reconstructed the tanker driver who they use to kill the two officers in a crash, both of whom are then recreated to do the assassinating. Just a tad long-winded.

Being one of the early episodes, Scarlet still experiences feelings of nausea in the presence of a Mysteron - in this instance it's on entering the conference with Major Brookes. However he doesn't seem to have learned much from his experience in Winged Assassin as he only realises Brookes is the bad guy after the latter starts swearing vengeance, which is a giveaway to anyone in earshot, nauseous or not. It's clear why the idea was dropped from later episodes, as it makes detection of the villains far too easy. Not only that, it's something he'd have to learn from after a few episodes, and with no guarantee that the series would be broadcast in sequence, the idea - not such a good one in any event - was dropped. Unfortunately, it seems to have been dropped before the end of the episode as Scarlet doesn't have a similar nausea attack when he's in the SPV with Colonel Storm later on. Ah, well. On the subject of inconsistencies, it's open to speculation as to what happens to the other delegates at the conference when Brookes explodes - they don't seem to have been provided with protective tubes - a lesson not to pick the cheap seats in the stalls perhaps. It must be pointed out that Spectrum were remiss in not checking on Colonel Storm more closely after Brookes blew himself up. Nor does it make much sense that having the Supreme Commander at gunpoint at the end of Part One, Storm does nothing - and again in the SPV he has a gun but shoots at Scarlet, ignoring his real target sitting opposite.

Such minor flaws tend to be forgiven due to Century 21's real strengths, the visuals. On the plus side, the lighting and movement of the puppet characters is very impressive, as is the moving walkway which has a very futuristic slant to it and makes the figures appear less static. The amount of work evident in those brief shots in the bazaar demonstrates the care that consistently went into creating the series, while the Angels' attack on the Unitron as it bombards Point 783 is what Century 21 is, in a nutshell - fast editing, great music, big explosions and unrelenting action. We even get a flamethrower attack on the base. Very impressive, as long as you're not on the receiving end of it. The sound effects also merit a special mention as they add so much to the atmosphere.

Point 783 is a snapshot of what Captain Scarlet is all about. It's visually and technically impressive, loud and exciting, yet perhaps just a tad flawed at script level. But still head and shoulders above the rest.