I can now see one of the advantages of having a different writer for each episode: they are genuinely different. This episode is - not in a bad way - very much of its time indeed, which if all of the episodes were like this would make the whole series seem more dated than it does. The references to Suez & a dog called Hitler, though, make the events of these episodes seem a very long time ago, compared to series such as The Avengers & most of the ones I like which avoid direct cultural references. Nor are the cultural references missing in this one: once again references which time it down almost to the year. There is even an obviously homosexual character, although this is not made explicit, which gives the impression that this episode is trying a bit hard for gritty realism. Nothing wrong with that, as such, but I would identify the repeated cultural references as a weakness because they distract from the main line of the plot.
On the other hand a somewhat straightforward whodunnit - or rather whydunnit - plot is lifted by the colourful characterisation. Of course as the episode progresses there is also revealed to be a science fiction element to this one, & the surreal touches such as the laughing bag give it an eccentric 60s feel. There is yet another cultural reference in Lottie & Hawksworth paraphrasing the nursery rhyme used in Agatha Christie's And Then There Were None:
Lottie: 'Five perishing VIPs snuffed out like candle wicks,'
Hawksworth: 'Another went & drowned himself.'
Lottie: 'That makes six.'
There are times when the characterisation is heavy-handed to the point of paraphrase. This works well in the case of the bank clerk, clearly at the end of his wits why people keep taking their money out:
Man in bank (when asked whether he is sure he wants to take out the large withdrawal he has asked for): 'Well it's my money, isn't it.'
Cashier: 'We just borrow it from our customers to play the stock market but they can have it back at any time.'
Unfortunately this heavy-handed approach is less successful in the case of the forgetful inventor, who is so forgetful he forgets the man in front of him isn't his daughter & gives him a kiss.
The larger-than-life characterisation works well with Lottie & Hawksworth, allowing their personalities to leap out from the screen loud & clear. I particularly love the bit where Lottie says:
'There's no rule that says a blackmailer has to ask for a nice round figure. It's just as good form to put the screws on your victim for eleven thousand, five hundred and eighty-five pounds and seven new pence as it is for twelve thousand. Especially if you know that's all he's got left.'
She then goes on to comment that she wants to know the perfume worn by the woman who's pulled off the same trick six times.
Anyway the colourful characterisation serves to distract from a relatively straightforward plot. Visually the episode is also effective, the sets actually don't don't feel like sets (on other epsiodes you can see them wobbling, & the interiors are very effective.
All in all I like this episode enormously, purely because it is overdone in so many ways, & especially in the invention to age people. I've also managed to watch it two nights running with a view to writing this post, without it grating on me & I think it's difficult to pay a TV programme a higher compliment than that.