The massive machine was carried in parts by a convoy of lorries

A convoy of lorries carried it in parts from Inverness to Fort Augustus.

Glendoe, in the hills above Loch Ness, is the first large-scale hydro-electric scheme to be built since 1957.

The Scottish and Southern Energy (SSE) project will mean the construction of a dam, a reservoir and turbines hidden in an underground power station.

The machine was transported early on Monday morning, with diversions in place to counter the closure of the northbound carriageway of the A82 between Inverness and Drumnadrochit.

SSE said the tunnel digger was expected to begin work almost immediately.

Explosive charge

Pupils at Kilchuimen Academy, Fort Augustus, have dubbed the 180 metre-long machine Eliza Jane.

Construction of the power station started at the site in February.

Prime Minister Tony Blair ignited an explosive charge to begin the creation of an 8km tunnel in the hills.

SSE said that while much of the project would be built in the hills overlooking Loch Ness and Fort Augustus, it would be visually discreet.

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.

An artist's impression of the Glendoe power station

Water will be collected from a new reservoir, about 600m above Loch Ness.

The power station will produce about 180 million units of electricity in a year of average rainfall.

Operating at maximum capacity, SSE said the scheme would be able to generate enough electricity to power 250,000 homes and should be fully operational by 2008.

It is hoped the construction phase could create 400 jobs.