IT was the flagship plan that would propel the Scottish capital to the forefront of the green transport revolution, but instead the original Edinburgh Tram project became a fiasco.

The first trams started running in 2014 three years late, with the project eventually costing £776m, well above the earlier practical estimate of £545m.

The scandal prompted then First Minister Alex Salmond to call an inquiry into what went wrong and the probe into the first part of the tram line, from Edinburgh Airport to York Place, is ongoing.

Its chairman, Lord Hardie, is expected to begin hearing evidence in public next month.

Herald View: New Edinburgh tram plan must learn lessons of past debacle

The inquiry will hear that vast tracts of the city along the route were excavated, refilled and dug up again as utilities such as electricity and water pipes were rerouted and foundations laid during the construction of the system, with residents claiming some streets in the West End finally resembled "a war zone".

The entire project ground to a halt for months after a row between the main contractors and the council, but it is claimed lessons were learned.

In Leith, firms prepared for trams that never arrived, the number that went out of business unquantifiable.

A compensation system for disruption will be put in place.

Adam McVey, council leader, said that "one of the big differences is that this process is aimed to be entirely delivered within this term of council".

He said: "If we think the business case is robust enough we move to phase two and see what comes back in terms of the contractors bidding, and whether they bid in line with that business case under budget and in an earlier time than we've put down.

"We are being conservative about this, we are being cautious, we are setting a very high barrier before we are going to push a big green button and say we are going to go for it."

Herald View: New Edinburgh tram plan must learn lessons of past debacle

In 2016, Edinburgh Trams had 5.6m passengers. By 2022, that is expected to reach 7.2m on the existing line, and if Edinburgh completes the line to Newhaven, the figure doubles to 13.7m.