LONDON: A Royal Navy frigate escorted a Russian warship on Christmas Day as it passed close to British territorial waters, the ministry of defence said Tuesday at a time of strained relations between London and Moscow. The HMS St Albans monitored the Russian frigate Admiral Gorshkov in the North Sea, “keeping track of its activity in areas of national interest,” it said in a statement. The St Albans, a Type 23 frigate, was deployed on Saturday to track the Russian vessel and would return to its Portsmouth base Tuesday. “I will not hesitate in defending our waters or tolerate any form of aggression,” defence minister Gavin Williamson said.