Sailors skipped festive celebrations to shadow a Russian vessel through the English Channel over Christmas.
Members of the Royal Navy were called in at "short notice" to crew the HMS Tyne to keep an eye on the Smolnyy Perekov as it passed close to UK territorial waters.
In fact it was so short notice one of the lookouts was wearing a Santa hat.
The Navy launched HMS Tyne from Portsmouth on Christmas Day as the Soviet era class of training vessel passed closeby.
The Portsmouth-based ship remained at sea on Christmas Day to monitor the Russian vessel, the Royal Navy said.
The HMS Tyne is primed to launch again today and throughout the holiday period, the force added.
Defence Secretary Ben Wallace thanked the crew who monitored the Russian vessel throughout the festive period.
He said: “I am grateful for the efforts of the crew of HMS Tyne, who have sailed on Christmas Eve, helping to safeguard or seas.
“This is yet another clear example of the tireless efforts of our Armed Forces, as they continue their tireless efforts to defend our country and our interests across the world."
Commander Jon Browett, HMS Tyne’s Commanding Officer, said crew travelled at short-notice from around the country to respond to the "short-notice" task.
He added" “Leaving our families at this time of year is especially difficult, but national security doesn’t stop for Christmas and as one of the duty units over the festive period we had bags packed and were ready to go.
“Our families understand our role and undoubtedly make a tangible contribution to national security through their continued support.
Thousands of sailors and Royal Marines were either on duty or on call ready to respond to tasks this Christmas.
