The expulsion of more than 400 suspected Russian spies from across Europe this year has struck the "most significant strategic blow" against Moscow in recent history and taken Vladimir Putin by surprise, Britain's domestic spy chief said.
In his annual update on the threat to Britain, Security Service (MI5) director General Ken McCallum also repeated warnings about Chinese attempts to influence lawmakers and those in public life, and Beijing's attempts to monitor and harass the Chinese diaspora.
McCallum said a massive number of Russian officials had been expelled from across the world including over 600 from Europe of which more than 400 were judged to be spies.
"This has struck the most significant strategic blow against the Russian Intelligence Services in recent European history," he said in a speech at MI5's London headquarters.
"And together with coordinated waves of sanctions, the scale has taken (Russian President) Putin by surprise."
He also described suggestions from Moscow that Britain was involved in blowing up Nord Stream gas pipelines as "silly claims".
He said the expulsion action followed a template set by Britain in the wake of the nerve agent poisoning of Sergei Skripal and his daughter Yulia in Salisbury, southern England, in 2018 which prompted a wave of diplomatic expulsions.
McCallum said this year Britain had refused more than 100 Russian diplomatic visa applications on national security grounds.
On China, the spy chief said the Chinese authorities were using all the means at their disposal to monitor and intimidate the Chinese diaspora.
He referenced an incident last month in Manchester, northern England, when a man who was protesting outside a Chinese consulate said he was dragged inside the grounds by masked men, and then kicked and punched.
"To intimidate and harass UK nationals or those who have made the UK their home cannot be tolerated," McCallum said.