Birmingham Airport officially scrapped plans for a second runway in 2007. But the idea has not been ruled out forever.

And supporters of the airport are increasingly talking about the benefits it would bring.

I don’t want to be alarmist about the prospect of a second runway at the airport, which hasn’t yet completed the long-awaited extension of its first runway.

If it ever happened it would be hugely controversial, and I think it’s safe to assume hugely unpopular, with the people living nearby.

There are no plans to build a second runway now. No announcement is imminent, certainly not so far as I am aware.

But it’s something of an elephant in the room. We know it’s still an option, but nobody wants to talk about it.

Birmingham Airport has won a very effective lobbying campaign to convince government ministers to make more use of “regional” airports.

Or perhaps I should say “airports outside the South-east”, as one if its goals is to be named a “national airport” and ditch the regional label.

This campaign has focused on the fact that Birmingham could double the number of passengers it serves, from nine million today to 18 million, without any new infrastructure.

And the planned extension of its existing runway will allow it to cater for 36 million passengers, and provide services all over the world (a larger runway allows larger planes, capable of crossing the globe).

But the airport’s campaign goes further than that. The gist of its message is that the Government should not build a new runway at Heathrow, nor go ahead with Boris Johnson’s plans for a brand new airport.

In other words, it is presenting itself as a potential answer to the question of how Britain can get the additional “hub” airport capacity it needs. That’s an airport where passengers change planes mid-journey.

If Birmingham is to fulfil that role, it would almost certainly need a second runway. And Midland MPs are quietly lobbying at Westminster for it to be allowed one.