Simon Hughes gives Vince Cable a detention.

As most of Westminster already knows, Vince Cable is hot to trot away from the Coalition. However, the Slog understands that there has been a serious outbreak of reality among Parliamentary Liberal Democrats. And although the Business Minister wears a perpetually long face (while seeming to invite the sack on a daily basis) there is no mood at all among his Commons colleagues for a revolt. Simmering discontent remains, but only fools are going to mount barricades while the LibDem poll score says 13%.

Simon Hughes signalled an end to the plotting last Wednesday by writing a high-profile piece for the Guardian about ‘ten weeks that have revitalised politics’. But his most recent soundbite won’t have resonated with the Tory Right; he told the media yesterday that “Our great party at last has the chance to make sure we build for the first time in decades a truly liberal Britain”. This would’ve been enough to send a green about the gills Norman Tebbit back to his bike shed.

However, an air of impermanence surrounds both the Coalition in general and Cable’s post in particular.

“Vince and Cameron had an almighty ding-dong before the mass exodus for India” says the Slog’s most trusted LibDem spy, “But Simon [Hughes] is insisting he [Vince] keep his powder dry.”

Cable and Hughes are natural allies: the Business Minister was a protege of John Smith’s in his Labour days, and Simon Hughes is still considered to be on the Left of the Party. Cable enthusiastically sponsored Hughes’ deputy leadership campaign, and the two men confer on a daily basis.

In the last 24 hours Cable has upped the ante again by calling for “the most liberal immigration policy possible” and demanding that firm Government action will follow unless the banks start lending to small business. The first of these is economically and politically naive, the second financially semi-literate: as long as the Treasury is selling gilts with higher yields than general interest rates at 0%, any commercially-minded bank would be mad not to buy them. He’d be better off talking to Mervyn King than Eric Daniels.

Despite increasing pressure from those memorably referred to by John Major as “the bastards”, David Cameron still retains the low political cunning of all those who are not very bright. For the Coalition to survive, he can’t and won’t fire Vince – and Simon Hughes can’t and won’t egg him on to resign.

So Mr Cable must stay back after school, and put his catapult away for a while.