A network of nine miles of tunnels has been dug Drill breakthrough

The 220-metre long machine, called Eliza Jane, made its breakthrough at Glendoe, Fort Augustus, on Monday.

Scottish and Southern Energy's plant above Loch Ness will generate power for 250,000 homes. The scheme is expected to begin operating later this year.

It is the first large-scale hydro-electric project since 1957.

The project will turn rainfall into green energy through a nine-mile network of tunnels linking a dam above Loch Ness to a generating station 2,000 feet below.

Scottish and Southern Energy said the project would pay for itself over the next 10 years.

Its chief executive, Ian Marchant, said: "The completion of this phase of the Glendoe development is significant.

"It is a unique, large and complex project and I am delighted with the progress that is being made."

In 2006, a convoy of lorries carried the tunnelling machine in parts from Inverness to Fort Augustus down the A82.

Pupils at Kilchuimen Academy, Fort Augustus, dubbed it the Eliza Jane.

Prime Minister Tony Blair ignited an explosive charge to begin the creation of the five-mile tunnel in hills above Loch Ness.

The scheme involves the construction of a 1,000m dam at the head of Glen Tarff and the building of an underground power station inside Borlum Hill.