Older readers will recall the moment Basil Fawlty - irritable as ever with his wife - drops into a sotto voce parody of Mastermind: "Next contestant, Mrs Sybil Fawlty from Torquay. Specialist subject: the bleeding obvious."
Some say the cultural commentator and general clever-clogs Malcolm Gladwell is a bit of a Sybil Fawlty. His books, they suggest, state the bleeding obvious. Thus, The Tipping Point told us that to change any system you have to find its tipping point - the tantalising juncture of critical mass that gives it sufficient momentum to change. Blink taught us that first impressions matter more than we realised. And What the Dog Saw includes an essay about teachers which I suspect tells us something we always thought: good teachers matter.
Gladwell cites the research of Eric Hanushek, an economist at Stanford University, who examines the difference between good and bad teachers. The students in the class of a bad teacher, says Hanushek, will learn half a year's worth of material, while those in the hands of a very good teacher will learn a year and a half's material. So the difference in how students do is startling: a gap of one year's progress in a single year.
Summarising the findings, Gladwell states: "Teacher effects dwarf school effects: your child is actually better off in a bad school with an excellent teacher than in an excellent school with a bad teacher. Teacher effects are also much stronger than class-size effects. You'd have to cut the average class almost in half to get the same boost that you'd get if you switched from an average teacher to a teacher in the 85th percentile".
So there it is: in case we hadn't realised, it all comes down to appointing good teachers.
The implication for those of us with responsibility for recruiting staff is not just how do we get the best into our schools, but whether we can know before they start working with us how good new teachers are.
Because Hanushek's research seems to raise questions about something that underpins government policy on training and recruitment - that the best teachers are the cleverest. This assumption lies in the proposal that every prospective teacher's GCSE grades in English and maths should be B rather than the current C and that their degree should be a second class or higher.
Better brains, the orthodoxy runs, make better teachers. I'm sceptical about such a simple causal link. In his long poem about the decline of rural life, the 18th-century poet Oliver Goldsmith described the village schoolmaster through the eyes of his fearful pupils:
... they gaz'd and still the wonder grew,
That one small head could carry all he knew.
We've all had teachers like that - people whose subject knowledge was vast and mesmerising. And some of them, in my own experience, were rubbish. If you can't explain things, if you can't keep control, if you can't ask questions in a way which provokes reluctant minds to learn, then you'd be best advised to avoid the classroom, a merciless arena for the temperamentally unsuited.
The American researcher Jacob Kounin says it's not intelligence that matters in teachers but what he calls "withitness". Watching teaches working with challenging classes, he notes that the difference between the effective and ineffective teacher is not how they stop bad behaviour at the end of an escalating chain of events, but whether they are "able to stop the chain before it started".
This is teacher withitness - that apparently mystical sense our best teachers have to know where to stand in a room, how to stand, when to pause, how to make the territory of the room their own. What they do prevents bad behaviour developing.
These are what we might call the micro-skills of teaching; they are bleeding obvious to some recruits and illusory to others. As Phil Beadle says in his new book How to Teach, you can detect a lesson's quality as soon as you walk into a classroom. A handful of simple clues says it all: if students are wearing coats, if their bags are on their desks, if they are holding pens when the teacher is talking, then it simply won't be a good lesson.
Which is where the Government is right to regard teaching as a craft, an apprenticeship. It's why we need to get more training into schools with would-be teachers learning to develop their "withitness" by serving as apprentices to our best teachers. It's why we need to get more rigorous in our appointment process, recognising that raising the intellectual bar for entry to the profession may not, after all, be the holy grail. And it's also why we need to stop being in denial about the fact that (as in any other profession) bad teachers exist and - given the startling impact they have on children's life chances - we need to be less tolerant of them.
How bleeding obvious is that?
Geoff Barton is headteacher of King Edward VI School, Bury St Edmunds.