The instant I heard how the NHS was treating Colette Mills and Debbie Hirst, the image came to me. Here we go again, I thought. Sootynomics.

When I was a boy I had a precious Sooty and Sweep record. You wouldn't think Sooty worked that well on record, would you? Not given that he was silent. But I thought it was hilarious, particularly the bit where the two puppets are ineptly preparing a dinner party. “What are you doing, Sooty?” exclaimed Harry Corbett as we hear woodwork noises. “Planing down a tree to make a cocktail stick?”

Funny though I found it then, I am sure I would have forgotten this moment of comic genius by now were it not for this - throughout my adult life I am continually coming across people planing down trees to make cocktail sticks.

The comedy comes, of course, from Sooty's failure to appreciate how big a tree is, how small a cocktail stick is and therefore how fruitless the effort is. Except that for Collette Mills and Debbie Hirst, Sootynomics isn't comic. It's tragic.

They both have cancer. They wish to benefit from a relatively new drug called Avastin, but the drug has not been approved for use by the NHS. It does do some good, but it is not regarded as cost-effective. So the two women decided that they would buy the drug themselves.

Fair enough? Apparently not. The two women have been told that if they pay for the drugs, NHS treatment will be denied to them. They have to pay for all their care privately, an impossibly large sum, or receive it all through the NHS. Alan Johnson, the Health Secretary, was firm on the subject. They cannot, he argued, “be treated on the NHS and then allowed, as part of the same episode and the same treatment, to pay money for more drugs”.

But the reason he gave was not a medical one - that drugs needed to be administered together by the same doctor on NHS time. Or a practical one - that it would be a bureaucratic nighmare to have some drugs for sale and some not. It wasn't a legal one either: it isn't at all clear that the law prevents this mixture of the NHS and private treatment Instead he said this of the request by these gravely ill women: “That way lies the end of the founding principles of the NHS.”

Now Mr Johnson is a compassionate man and an intelligent one, too. He's not, in my experience, generally dogmatic. So what on earth possesses him to deny cancer treatment to these terribly sick patients? Where could such an idea come from? Sootynomics.

Last year was the 50th anniversary of Tony Crosland's book, The Future of Socialism. While re-reading what was, when it was published, one of the most important books of social democratic thinking, I was struck by how dated it had become. Crosland spent half the book in earnest dispute with people advancing ideas that are, to the modern eye, completely ridiculous. He patiently explains, for instance, over an entire chapter, why guild socialism - a barely comprehensible scheme in which trade groups control industry - wouldn't be a bright idea.

What has changed over the past 50 years is this: we now appreciate, or at least have some inkling, how big and how complicated the world is. When there are staff employed in the occupational therapy unit of the IT centre of the people who make the dye that colours sliced bread packaging, how exactly does guild socialism work? The idea of a fully planned economy, painstakingly criticised by Crosland, now needs little effort to refute. It has simply fallen away.

Yet there remains an extraordinary amount of public policy confidently advanced without any idea of the massive contrast between the size and complexity of the world and the puny measure being proposed, without any understanding that the world rages on like the sea - unstoppable, uncontrollable.

The absurd idea, for instance, that you can tackle obesity by banning food advertisements on children's television (an apt example of Sootynomics, come to think of it) or stop climate change by using fewer carrier bags at the supermarket. I remember one of my colleagues calling for a boycott of Tesco because it was killing the high street. The last time I looked, Tesco was still trading.

Alan Johnson's NHS ruling is a perfect example of the same syndrome. What is the fundamental principle whose end he fears? Not that care should be free at the point of use, since he already believes that to use Avastin, you must pay for it. No, the principle to which he clings is that all patients should receive the same care. There should be equality.

Do you see what I mean when I say it would be comic if it wasn't a tragedy? Mr Johnson looks at the world with its vast disparities in wealth, with its teeming masses and its warzones and its starving slums and its clipped suburbs and thinks he can make the world more equal by preventing a couple of women buying Avastin.

Actually, never mind the starving slums and the warzones, there isn't even equality inside the NHS. There are cancer drugs you can have prescribed in Scotland that you can't have prescribed in England. You can pay for some dental services while receiving others on the NHS. You can receive two different but related treatments and pay for one of them as long as you don't have the treatments together in one place as one episode.

Alan Johnson is trying to hold a line that cannot be held. As more expensive drugs become available and are deemed “not cost-effective” the Mills and Hirsts will multiply. The offence against their rights will be seen increasingly as unacceptable and the pursuit of an elusive equality ever more obviously futile.

You may as well stop planing down the tree now, Mr Johnson.

daniel.finkelstein@thetimes.co.uk

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