Nine Royal Navy vessels have shadowed seven Russian warships after detecting "unusually high levels of activity" in the Channel and North Sea.
It comes as the Royal Navy has been preparing to help the NHS and other government departments deal with the coronavirus crisis.
Royal Navy sailors and aircrew have been monitoring every movement of the Russian ships using state-of-the-art radar, surveillance cameras and sensors, allowing them to track their course and speed as they passed the British Isles.
They were supported by Merlin and Wildcat helicopters of 814 and 815 Naval Air Squadrons.
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Portsmouth-based HMS Tyne spent more than a week working in the English Channel keeping a close eye on the Russian vessels as they passed the south coast.
Lieutenant Nick Ward, HMS Tyne's executive officer, said: "As the Armed Forces are helping the NHS save lives in the UK, it's essential the Navy continues to deliver the tasks we have always performed to help keep Britain safe."
He added that the work "represents one of the many roles our patrol vessels perform in support of the Royal Navy's commitments".
"This is our core business and represents an enduring commitment to uphold the security of the UK," he said.
During the operations, three Steregushchiy-class corvettes, two Ropucha-class landing ships and two Admiral Grigorovich-class frigates were observed, as well as their supporting auxiliary ships and tugs.
HMS Sutherland watched on as the Merlin helicopter carried out a number of intelligence-gathering sorties over the Russian ships as they passed through the Channel.
HMS Sutherland's operations officer, Lieutenant Hannah Lee, said: "Our successful integration into the maritime group proves our ability to adapt to task group operations at short notice.
"Having proved we can work together and contributed once again to NATO operations, we now look to return to UK national tasks in support of the very highest defence priorities."
Meanwhile, the Royal Navy's logistics specialists and military planners have been working with the wider Armed Forces to help the coronavirus response effort.
Sky News' foreign affairs editor Deborah Haynes said: "This really underlines concerns by senior officials about how this coronavirus pandemic across the world is a huge distraction for governments and could potentially be exploited by adversaries.
"And that's why, while you've got up to 20,000 military personnel on standby to help the government in its COVID-19 response, you have also got preparations underway to ensure that critical military operations such as the Royal Navy shadowing Russian vessels off the coast are able to continue."