But...if you have a rotten script there is nothing you can do about it. And it's that awful moment for a fan, when you've just enjoyed something exquisite, unique even, when next week you can't believe how rotten the whole thing's gone. Think - from 'Marco Polo' to 'Keys of Marinus', from 'Celestial Toymaker' to 'Gunfighters', from 'Sea Devils' to 'Time Monster', from 'Mandragora' to 'Hand of Fear' from 'Sunmakers' to 'Underworld', from 'City of Death' to 'Creature from the Pit'. And then consider - the whole of Season 18 (in which I virtually include 'Castrovalva' anyway) to this.

Leaden, lumpen dialogue and plot development which makes a total mockery of most of the regular cast. Tegan becomes a brainless panicky bimbo, Adric gets convinced by the most implausible villain since the Nimon, and the Doctor dashes about like Biggles dressed like Andy Pandy. Poor old Nyssa gets ordered around by Adric (as well as being called 'only a girl' blimey people keep mistaking Nyssa for a child - are there no opticians in space?) and has to admit to being frightened, get hypnotised, get rescued, get hypnotised again, get rescued again, ask Adric for help and finally faint. Of course it is to Sarah Sutton's credit that she makes the most of the two opportunities she's given - to stand up to Monarch and Adric (and the only good line of the show 'what about love?') and to save the Doctor's life (you start to understand Davison's fondness for this character's uncomplicated devotion to his Doctor). But really, I mean - 'Pass the Sodium Chloride', from a show that gave us 'With my eyes, no, but, in my philosophy...' only five days earlier.

Then there is Tegan's sudden ability to draw, speak native Aborigine from x trillion years ago, the nonesense about the poison, the frogs and the miniaturised androids. I won't bother asking all those 'why does....' questions as there are so many of them, I can only comment that it doesn't say much for a show when the title doesn't even make sense - Four what to Doomsday? Days? If so, why not say it? Might be four androids to Doomsday, four crew members to Doomsday, four episodes (or four of the longest half hours of your life...). Personally, I think it was 'Four Days to Doomsday' and the typist missed a word out for the titles... If this was the quality of scripts that Bidmead was being sent, no wonder he claims he wrote 90% of season 18, and how badly he is missed and so quickly! If you look at the next few seasons as a whole, it all starts to go wrong from here on, but it's only with 'Time-Flight' that the rot's confirmed and only with 'Twin Dilemma' that the disease becomes inoperable. But you have to wonder what the BBC was doing, putting a trainee in as a script editor - but it confirms that the post was undervalued as Bidmead said and that gloss mattered more than quality.