It was, said John Swinney, “desirable but not essential”. When the then finance secretary binned Glasgow’s Airport Rail Link eight years ago he felt he had saved the public purse a fortune.

GARL, as the ill-fated scheme was called, was, in SNP eyes, one of the old vanity transport projects they had inherited from their LibLab predecessors. It was Glasgow’s Edinburgh Trams.

For Labour Mr Swinney’s decision was a ‘dagger at the heart of Glasgow’. It gave them ammo to accuse the SNP of letting Scotland’s biggest city.

It also, a cynic might add, saved them from the potential risk of being blamed for an expensive white elephant. Bad headlines continued: the aborted GARL had cost a wasted fortune in planning and land purchases.

Scroll forward to 2014 and new money appeared, a new City Deal. Plans for a rail link were resurrected, but with a cheaper tram to run on the rails to Paisley with a connection on to tram lines at the airport.

Last year the councillors responsible for spending City Deal money backed that scheme, called GAAP. Transport Scotland commissioned an independent report. It was delivered in August but not widely shared. Its findings, according to copy obtained by The Herald, were damning.

Insiders stress it would be almost impossible for the government - or councils - to sign off any spending another penny on a project that would interfere with core rail services so much it would do more harm than good.

So where does that leave a link to the airport? Dead? Not quite.

Despite all the previous politics, there is now a consensus emerging for some kind of service. Indeed, this used to be an area politicians agreed on. When The Herald first reported on calls for a rail link - back in the 1990s - all parties wanted something. But as part of a wider scheme to boost station and line capacity in Glasgow. The city’s two big stations - and lines north and south of the Clyde - are not linked.

Plans for a crossrail or a giant underground station, widely discussed until 15 years or so ago, are long gone. That means any heavy rail link has an obvious problem: poor connectivity to the rest of Scotland’s transport network.

As consultants stress, the current bus service from the airport may still be quicker to Queen Street and beyond than the proposed train tram.

GARL used to be one of a vast number of transport ‘priorities’ from transport quangos and and council officials in Glasgow.

There was another “priority”: some kind of fixed link from the city centre to what used to be called the Southern General hospital.

Now the Queen Elizabeth Hospital, it has serious transport and parking problems. And, transport insiders stress, is on the way to the airport.

The West has a billion to spend under the City Deal. Will we see council and government chiefs dust off an old priority? After all, a tram to the hospital, Braehead, Renfrew and the Airport may well be “essential” as well as “desirable”.