So, Ed Balls is rethinking his plans to turn 11 million Britons into paedophile suspects: not much of a surprise, given the near-universal derision that greeted it. The plan may need "adjustments", he says, which we can take as code for a total retreat: yet another crack-brained New Labour notion is about to bite the dust – and so it should. The Vetting and Barring Scheme requires everyone having regular contact with children, in any context outside a family one, to be approved by the Government after registering on a state-run database.
Youth club leaders, choirmasters, Brown Owls – even members of parental lift-sharing schemes –would all come under the cosh, paying £64 a head to pre-emptively clear their name. Philip Pullman is one of several children's authors who have said they will withdraw their classroom services, if this rule comes into force.
Yet, as anyone could have told Balls and co, the scheme won't make children any safer, except by accident: Ian Huntley actually had been listed, but word had just not reached the Cambridgeshire police. And the punitive effect of publicly-voiced suspicions which later proved unfounded would bear down heavily on any adult unfortunate enough to be investigated.
Balls says the plan may need "adjustments", but that is clearly an understatement for what may soon befall it.
As many commentators have pointed out, this scheme reflects an insidious new orthodoxy which holds that only authorised adults have any business engaging with children. The fear of being accused of improper conduct now prevents adults in many spheres from exercising the benign guardianship that used to be routine.
The most extreme expression of this fear, cited by the commentator Jenni Russell, is a draft guide for teachers at the Purcell school for young musicians, which presents the situation in a breathtakingly lurid light: "Some adolescents experience periods of profound emotional disturbance and turmoil when they may be unable to differentiate between fantasy and reality. They may be temporarily insane. They can thus present a danger to even the most careful of teachers," it says.
The advice that follows recommends an almost paranoid circumspection in all tutorial dealings, and ends with the sentence: "It is helpful to think of current pupils as clients, rather than friends, as a doctor does." You'd laugh, if it wasn't so sad.
Peter Crook, head of this distinguished institution, points out with exasperation that these guidelines have no official status: they were mere backroom brainstorming, just a draft. But the guidelines the school has adopted do indicate that such fears are real enough. They say that they "are as much about protecting ourselves as they are about protecting the children", and observe that one-to-one instrumental tuition is a "particular risk".
One of their key requirements – which all music schools now follow – is that such lessons must take place in a room with a window to the corridor, which "must not be covered". If lessons take place outside school premises, another adult must be within earshot; if in doubt, when having a one-to-one meeting, "leave the door open"; "if you need to take an unaccompanied child in your car, be sure the journey is known to another member of staff or the child's parents".
While it's easy to mock such zealousness, music-teaching is by its nature a high-risk zone. The improperly amorous music teacher is one of the stock characters of Italian opera, as in The barber of Seville; the list of composers taking sexual advantage of their pupils starts with rumours of Vivaldi preying on the girls in his musical convent, and goes on for ever.
Beethoven habitually fell for his female piano pupils; Schubert's four-hand piano music was a lovely way to get up close and personal with his young protégées. Robert Schumann's love affair with the 10-years-younger Clara Wieck – which blossomed into marriage – began when she was in her mid-teens. Tchaikovsky would have been struck off time and again, had he lived now, for repeated amorous advances to his young male relatives and conservatoire pupils. "My beauty is a gymnasium student, and must finish her examinations," he wrote of a boy who had taken his fancy.
And this tradition still pervades the music scene, if not as flagrantly as a few decades ago. I know of some happy marriages that began as clandestine affairs between music students and professors; I also know of some unhappy victims of sexual harassment by conductors and choirmasters. Part of the problem lies in the power relationships involved. But part of it – which shouldn't be seen only as a problem – lies in the sheer passion the shared pursuit of musical excellence can arouse. Music, as Plato famously declared, is dangerous stuff.