Smoke could be seen pouring out of a submarine in Scotland this afternoon – but the images turned out to be no cause for alarm.
It led to intense speculation on Twitter with one user questioning whether it was ablaze.
They said: “Nuclear submarine apparently on fire (or at least emitting a lot of smoke) near Helensburgh.”
Another tweet said: “Folks submarine seen in the sea off Helensburgh… smoke pouring from it… six tugs in attendance.. pics to follow.”
But the Royal Navy said the submarine was just doing a “cold move”, which involves moving the vehicle around the harbour without using its own propellers.
The smoke is from the diesel engine starting up and running.
It comes after Britain’s deadliest fleet of warships in 20 years gathered in the North Sea in a massive show of force against Russia and China this month.
The UK Carrier Strike Group – plus warships, fighter jets and helicopters from the US and the Netherlands – is practising for high seas warfare.
At the centre of the heavily-armed flotilla is our biggest-ever warship the aircraft carrier HMS Queen Elizabeth laden with top of the range American and British F-35B fighter jets.
The carrier was the dream child of British politicians in the late 1990’s, took 24 years of planning and building and now she is set for her first major high seas mission some time next year.