At what point will the Cable snap?

It is the question that may determine the longevity of this government. When will the man lionised as an economic prophet in much of the UK, winner of Channel 4’s Chancellors debate, decide the coalition has compromised his principles too far?

The short answer is ‘not any time soon’, but my assessment is that does not mean ‘never’. In recent weeks I have been tracking the full array of Vince Cable’s dissent. It is somewhat impressive, and today, the day of his conference speech is as good a day as ever to look back.

Let me list the four issues where he is musing at the limits of ministerial collective responsibility. The immigration cap. Sir Philip Green’s appointment as ‘austerity tsar’. Tuition fees. State of the economy and the chances of a ‘double dip’ recession. Then there are another four issues which could move into this category. The pace of deficit reduction. Sharp cuts to the business department budget. Banking reform. Tax avoidance and evasion.

As one senior coalition-loving Lib Dem told me: “Vince hasn’t quite got used to the fact that he is no longer treasury spokesman with a licence to proclaim his view on every subject.”

Actually I think there is another reason. The business secretary believes he is actually running a department of economics, in the German ‘twin-headed’ style of economic governance, as a counterweight to the treasury.  He told me this on camera in July. And economics is a lens on a whole sweep of policy, rather than a defined and discrete area like transport or housing.  It is the letters on his desk from businessmen that are motivating his intervention on the immigration cap.

Do not underestimate the last two issues in the Cable-snapping list. The business secretary may be tested by new efforts from Britain’s low tax dependencies in the Channel Islands and elsewhere for a change to the Labour Treasury’s anti-avoidance efforts. On banking reform, I have spoken to senior bankers who are at once slightly scared and bemused by the business secretary’s lack of engagement with them. They genuinely fear his influence over a harsh outcome against Britain’s existing banking structure.

And there is the rub. This is not unhelpful to the government. Mr Cable seems to have internalised the job of opposition within the government. But it is surely helpful to have someone within the tent sharing widely-held concerns about banking boom as austerity bites, than not. Remember it was George Osborne who made the running against bankers’ bonuses a year ago. As the chancellor told me last month, the coalition has internal disagreements and grown-up debate, a contrast to the ‘unhealthy pantomime’ of Blair versus Brown.

So that is why, despite the differences, this Cable remains tethered to this Government.