A Royal Navy ship has docked in Harwich for the first time since the 1960s.
HMS Severn anchored in the Essex port on Sunday for a crew change and was due to depart on Wednesday.
The 80m-long (262ft) vessel is used for patrols around the UK coastline, where responding to Russian ships has become an increasingly common task.
Lt Cdr Dominic Jacob, its executive officer, said crews wanted to make sure the vessels were not involved in “nefarious activity”.
“We quite often get tasked on to Russian ships which are at sea – frigates, destroyers and such like,” he said.
“We shadow them within the UK area of responsibility to make sure they don’t get up to any nefarious activity and just to act as a deterrent.”
On Saturday, the Royal Navy said its warships and helicopters spent 21 days monitoring Russian activity in UK waters and the North Atlantic throughout July – a 25% rise on the previous year.