BT is to invest £8 million in bringing superfast broadband to the Highlands of Scotland by lighting up capacity in a fibre optic cable running from Inverness to Orkney and Shetland.

Almost 1,000km of fibre cable, including 400km laid beneath the sea, will be up and running by early next year.

The investment is expected to deliver download speeds of “up to 20 megabits per second” – more than double the fastest speed currently available from the company.

The existing microwave radio links that currently serve Orkney and Shetland will be kept as a back-up.

Brendan Dick, director of BT Scotland, announced the project at a public meeting in Shetland.

“This significant investment demonstrates BT’s ongoing commitment to the Highlands and Islands of Scotland,” he said.

“By investing £8 million in this fibre spine for Orkney, Shetland and the north of Scotland, BT is laying the building blocks for any future deployment of fibre broadband.”

The company said that seven towns – Kirkwall, Lerwick, Dingwall, Tain, Thurso, Alness and Invergordon – will all have access faster broadband over subsidiary copper lines, thanks to its “ambitious” plan.

Testing on the network has taken place at BT's laboratories in Suffolk, and a service for reporting faults has also been set up by the firm in Orkney and Shetland.

Meanwhile, BT has been awarded a multimillion-pound contract to provide superfast broadband in Norfolk, and looks set to win a similar contract in Suffolk, after rival Fujitsu confirmed it has withdrawn from the bidding process.

To date, BT has won all the contracts it has bid for as part of the Broadband Delivery UK (BDUK) scheme, as Fujitsu has reportedly been branded as too ‘high risk’ to take on new government work.