Last Night's Viewing: The Bletchley Circle, ITV1 Hilary Devey: Women at the Top, BBC2

There was a neat moment early in The Bletchley Circle that it's hard to know who to credit to. The drama is based around a group of former Station X cryptographers who apply their wartime skills to tracking down a killer. In a short pre-credit sequence you see them during the war as one of them, Susan, spots a pattern in the intercepts that turns out to be strategically critical.

"All those troops are on the move now because of us," she says wonderingly to a friend as they prepare to go to sleep that night. "Not bad for a few ordinary girls in a tin hut." And then the credits roll, rather literally in this case with a close-up of the revolving drums of the bombe, the primitive computer built to assist in breaking the Enigma code.

What you see next looks like a cipher, a meaningless string of numbers and letters. And then you see the wool and the needles. That's Susan's plight right there. Reduced from weaving world history to working out knitting patterns. And what her friend replies – "You couldn't be ordinary if you tried" – is the cue for the drama that follows.

Susan really does try. She gets married, has children, keeps house and knits. But it isn't quite enough to satisfy her and she feeds her passion for unravelling by following the details of a series of local murders, creating a kind of crime board on the back of her dressing-table mirror. When she thinks she's spotted another pattern she goes to the police. Naturally, she encounters male condescension, failure and a galling consolation from her careerist mouse of a husband: "I'll buy you a new book of puzzles," he says. So Susan decides to go it alone in tracking a man she believes is a serial killer and calls in the assistance of her wartime friends: Millie is "good with maps", Jean can boss her way into official archives and Lucy functions as a kind of human hard-drive, absorbing masses of facts and spitting them back out on demand.

It's a good idea, powering a crime mystery with the frustrated intelligence of clever women. But it needed to be a little cleverer itself about the intractability of the world it was depicting. You could just about believe that Susan's husband might get her a meeting with a senior police officer to lay out her theory. But her explanation of her thinking was then so sketchy that it seemed incredible he would reassign policemen to search where she'd directed. And the post-war London shown here is at one moment crisply real – as when the women work their way through local train timetables to try and work out how the killer is selecting his victims – and at the next magically pliable.

The women just seem to stumble on the location of the final victim by lucky chance, and there's no exploration of the complications that might follow on such a discovery. Writers should remember that audiences are often much smarter than they're given credit for. They can't always be fobbed off with a book of puzzles.

Female empowerment was also the theme of Hilary Devey: Women at the Top in which the Cruella de Vil type from Dragons' Den explored women's continued exclusion from senior jobs. The gimmick here was that Devey began by thinking the only problem was female commitment. If she could do it, she said, so could anyone. There was no such thing as the glass ceiling, she announced, and if women had to work harder to achieve the same as men, well... tough. She had her mind changed (I think), not least by the discovery that the most gender-balanced departments in her own business were delivering the best profit. If you're a woman and you fancy the idea of driving a fork lift truck, it might be worth giving her a call.

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