BT is laying a fibre-optic submarine cable between Orkney and the Scottish mainland. The 70-kilometre cable will run from Skaill Bay in Orkney, under the Pentland Firth, to Dunnet Bay, about five miles east of Thurso.

BT is laying a fibre-optic submarine cable between Orkney and the Scottish mainland.

The 70-kilometre cable will run from Skaill Bay in Orkney, under the Pentland Firth, to Dunnet Bay, about five miles east of Thurso.

BT has awarded the contract to independent marine engineering company Global Marine Systems, which began installing the cable last week.

Weather permitting, the work should take around three weeks.

Global Marine's cableship CS Sovereign is using its submersible plough and remotely operated vehicle systems to install the cable up to one metre below the seabed.

The new cable is the latest step towards bringing BT's "21 Century Network" (21CN) to the islands.

BT has already reached agreement with Faroese Telecom to share part of a new fibre-optic submarine cable which has been laid between the Faroe Islands, Orkney and Shetland and the Scottish mainland.

That cable comes ashore at Banff.

Brendan Dick, director, of BT Scotland, said of the new cable: "This is another major step forward in the massive amount of preparatory work we are progressing so that people living in the Northern Isles can share in the benefits that our next-generation network will bring."

He added: "It's one of the biggest projects BT has ever undertaken and much more work will have to be done before 21CN comes to Orkney and Shetland. Nearly 60 exchanges in the islands, from the largest to the smallest, will have existing equipment removed and replaced with 21st century kit.

"And it will be well worth the wait, because every exchange, no matter how remote, will have the same capability as a city centre exchange."

Gabriel Ruhan, chief executive of Global Marine Systems, said: "The new subsea cable, and 21CN in general, will enable BT's customers to meet demand from their customers for new feature-rich multi media and multi-play services.

"We are very pleased to be a part of such a project and our long-standing relationship and past success with BT will help us as we move forward."

He said the project followed on from Global Marine's successful installation in May of a new cable system connecting the UK with Guernsey in the Channel Islands.