The expulsion this year of more than 400 people from Europe suspected of being spies for Russia has dealt Moscow its "most significant strategic blow" in recent years and surprised Vladimir Putin, the head of Britain's spy agency said.
In his annual report on threats to Britain, MI5 Director General Ken McCallum also reiterated warnings about Chinese efforts to influence lawmakers and public figures, as well as Beijing's efforts to keep surveillance and threatening the Chinese diaspora.
Mr McCallum said a large number of Russian officials had been expelled from around the world, more than 600 from Europe, of whom around 400 were accused of being spies.
"This has been the most significant strategic strike against Russian espionage in recent times in Europe," he said Wednesday during a meeting at MI5 headquarters in London. "Together with the coordinated wave of sanctions, these actions have catch Putin by surprise".
He said the response followed the formula set by Britain after the nerve agent poisoning of Sergei Skripal and his daughter Yulia in Salisbury in southern England in 2018, which triggered a wave of diplomatic expulsions.
Mr McCallum said Britain had rejected more than 100 applications for Russian diplomatic visas on national security grounds.
Britain has been one of Ukraine's strongest supporters since the Russian aggression. Mr McCallum said the importance of this support was reflected by Moscow's absurd claims that Britain was involved in blowing up the Nord Stream gas pipeline in September.
"What is important is that the UK is prepared for Russian aggression that could continue for years," he said.
THE LONG GAME OF BEIJING
While Russian aggression on Ukraine is in the spotlight, British intelligence agencies have named China as Britain's biggest long-term threat.
Mr McCallum said Beijing was "playing the long game" in trying to manipulate opinion by keeping in touch not only with senior lawmakers but also with those just starting out in public careers, such as local councillors, who could later become members of parliament.
"If they are prepared to invest this amount of patience and funds, this amount of effort to maintain an incredibly large number of contacts throughout our system with the aim of recruiting them, this is a huge and long-term challenge." he said.
The British spy chief also said that Chinese authorities are monitoring and intimidating the Chinese diaspora, with actions ranging from forced repatriation to attacks on them.
He cited an incident last month in Manchester, northern England, when a man protesting outside a Chinese consulate said he was dragged inside by masked men, who then kicked and punched him.
"It cannot be tolerated that UK citizens, or those who have made the UK their home, are intimidated and harassed," Mr McCallum said.
China has dismissed such claims as baseless, accusing critics of provocation.
Meanwhile, terrorism still remains a major threat, with 37 plots foiled since 2017 and eight since last June, Mr McCallum said. While Islamist militants remained the main problem, there has been a rise in the far right demanding firearms, including 3D-printed weapons.
"We are seeing a growing number of far-right influencers operating globally, fueling grievances and reinforcing conspiracy theories," he said. "This problem seems to last."