Review for all 4 episodes:
While I almost admire the bravery of giving the 6th Doctor such a shockingly different characterisation the way it is done completely alienates me today as much as it did when I watched it on its original transmission. I had loved Peter Davison's 5th Doctor for his heroically good nature epitomised more than ever with him eventually sacrificing himself to save his companion Peri. For him to regenerate into the 6th Doctor and be actually trying to strangle the person he died to save within the first 20 minutes as well as treating her with such disrespect and disdain is just far too jarring. It could possibly have worked if the writing and direction was to make it purely a short bad effect of regeneration making him deranged and portray it skillfully enough. It is not done well at all because the writing makes the 6th Doctor just seem like a totally unpleasant character. He continues to be a pompous, selfish, cowardly petulant, egotist with no compassion for the whole story and with a tendency to violence totally out of keeping with The Doctor. Indeed much of his tenure is blighted by aspects of these unpleasant traits continuing to appear. It does not allow for it to be excused as a temporary post regeneration trauma. Not much of this is Colin Baker's fault and in fact his acting in the first part of this story is admirable. Sadly the characterisation is bad and Colin's acting comes across as over the top, annoying and unengaging as a result. If he had simply been a darker Doctor it could have been interesting but the way it is done is just bad.
The first episode features him strangling Peri and being a conceited bully. The second episode makes it even worse showing him as a coward offering Peri as 'the one to blame' when threatened and so many awful character aspects are shown throughout the story. Even without that the story is lame. Twins with mathematical genius are kidnapped and a race of giant gastropods have taken over a planet. The twins are not well acted and are irritating, the gastropods are silly and the story is both boring and badly put together. There are silly plot elements throughout such as The Doctor leaving a random person in the TARDIS with his gun. Maurice Denham is a very very good actor indeed but there is no material to use even his potential as a guest character. The rest is unsatisfactory including Peri whose performance adds to the other annoying elements.
Baker's acting is sometimes shining through the bad characterisation, Denham is as good as he could be and there are a couple of minor elements of usual Doctor Who interest but overall this is not fun, not good enough quality for the show's usual standards and is makes the 6th Doctor unlikable.
This adventure brings season 21 down. They could have at least let Davison see out the season and left Baker to start his own season fresh. Very disappointing. 3 to 3.5/10 if you take whatever positives you can.