You’ve got to feel sorry for Transport Secretary Justine Greening, who’s coming under increasing pressure from her Conservative colleagues for the crime of defending Conservative policy.

Her refusal to back a third runway at Heathrow has put her in the line of fire, with MPs including former Environment Minister Tim Yeo condemning the stance.

Other Tory MPs are also demanding a rethink, including Conservative members of the All-Party Group Parliamentary Aviation Group, which has published a report warning that failure to expand Heathrow is harming the economy.

This provoked a chilly response from Birmingham Airport, which is trying to convince the Government to make better use of regional airports instead.

The airport has even purchased advertising space at Westminster underground station, used by many MPs, to display a poster urging Ministers not to “put all your eggs in one basket” – the basket being Heathrow.

Paul Kehoe, Chief Executive of Birmingham Airport, said: “It is frustrating that this report fails to look beyond Heathrow-centric aviation orthodoxy that is stifling proper debate in this country ... we need a fresh approach to UK aviation policy.”

The Conservative election manifesto specifically ruled out a third runway at Heathrow, and the party won’t even be able to blame the Lib Dems if it breaks its promise on the issue. They are firmly in Birmingham’s corner.

In fact, Ms Greening appears very sympathetic to Birmingham’s argument that it makes sense to use the spare capacity which already exists at regional airports rather than building yet more expensive new infrastructure in the wealthy south. That’s not to say Birmingham Airport will get everything it wants when the Government finally publishes a long-awaited aviation review – expected in September – but it won’t be ignored.

There’s reshuffle talk at Westminster and some speculation that Ms Greening may be for the chop, or a sideways move at best. It would look very unfair if that turned out to be true.