David Blunkett did finally acknowledge the burden of covering for non-existent teachers and announced yet more emergency measures to entice former teachers back to the classroom. Until now, ministers have appeared not to accept the true scale of secondary vacancies.

It was clear last year that unfilled posts were increasing, particularly in schools under “improve or else” threats. Yet the secondary vacancy rate in January was still only 0.8 per cent, equivalent to 1,645 teachers. But these only cover vacancies advertised on the day of the survey and are widely regarded as an undercount. The TES’s own survey the same month identified 2,410 full-time permanent vacancies - 47 per cent more - in less than a quarter of all secondary schools.

Had the real seriousness of the situation been acknowledged earlier, measures to tackle the shortages might have stood a better chanc of persuading teachers to hold off their action. Ministers might also have been more inclined to listen to teachers’ grievances - particularly when the independent pay review body called for an inquiry into excessive workloads. Then, at least, some of the professional goodwill that has been needlessly squandered might have been salvaged.

Instead, David Blunkett chose offence as the best defence. In doing so he bolstered the vote for no-cover when previous turn-outs had been poor, drove more disillusioned teachers from the classroom and provoked doubts among those considering teaching as a career.

The unions might eventually have to settle for an inquiry; no one can limit contact hours - in the short term at least - without non-existent extra teachers. But for now, with ministers mesmerised by the election and union leaders hog-tied by next month’s annual conferences, we are stuck with a damaging stalemate that threatens, not just the excellent progress schools have made, but the new trust and confidence in the profession that was beginning to emerge.