A subsea bomb squad yesterday started its operation to detonate a Second World War mine lying under a major North Sea gas pipeline.

Oil giant Shell is removing an unexploded ordnance from the sea bed – about 62 miles off St Fergus, Aberdeenshire – almost 20 years after it was discovered.

The complex operation is expected to take up to three days and will use state-of-the-art technology.

The mine has been monitored by the firm since it was discovered at the FLAGS pipeline (Far North Liquids and Associated Gas System) in 1993 – a line that is responsible for up to 5% of the UK's daily gas supply.

Previous assessments had concluded it was safer for the mine to be left in place.