The trouble with revolutions - apart from general mayhem, unintended bloodshed and having to address the neighbours as "comrades" - is that they are easily hijacked. Every Kerensky, Chiang Kai-shek or Snowball risks being eclipsed by a Lenin, Mao or Napoleon. So it is with Michael Gove and his school reforms.
Reports surfaced last week suggesting that the Government would allow grammar schools to create "satellites", despite a pre-election pledge that there would be no expansion of selective education. Mr Gove, so the argument went, had "let the genie out of the bottle" with his free schools and it was only logical that those freedoms should be extended to grammars. Asked by Tory MPs if he would allow them to expand, he replied: "My foot is hovering over the pedal."
One can only hope that he had in mind the brake rather than the accelerator. It would be a catastrophe for the country - and for Mr Gove's reforms - if he heeded the calls from the Tory back benches. A decade into the 21st century, it seems incredible that we need to restate the case against state selection at 11. But needs must when the devil drives.
Advocates argue that grammars achieve excellent academic results and aid social mobility. The first contention is banal - selecting the brightest early and citing their final good grades as proof of superiority is a bit like Harrods feeling smug because its customers are wealthier than Primark's. The second is untrue: only a tiny percentage of their pupils are now on free school meals, while the myth that grammars were responsible for the relatively rapid social progress of pupils born in 1958 compared with those born in 1970 is just that, a myth - most schools were already comprehensive when the earlier generation left their primaries. Grammar schools concentrate the middle class; they do not liberate the disadvantaged.
Add to the charge sheet the fact that most successful foreign education systems are non-selective and that branding the vast majority of youngsters failures at 11 might be a bit premature as well as a tad cruel and the argument for grammars becomes even less convincing.
For undecided Conservatives there is one other - grammar schools are distinctly un-Tory. A selective system is a rigged market. It puts a floor under mediocre grammars, because however poorly they perform they will always be in the top tier - and it caps the potential of ambitious non-grammars, because they cannot gain access to it. Selection allows the supplier to choose the customer, rather than forcing them to compete for custom. It's almost Soviet. Far from being a logical extension to Mr Gove's reforms, an expansion of grammar schools would almost certainly derail them. Fortunately, faced with a brick wall, most drivers quickly realise that when it comes to pedals, they don't really have an option.