Paul Rimmer, a British security expert, says his country is swiftly releasing intelligence on Russia's invasion of Ukraine with the aim of weakening Russia's position.

Rimmer, a visiting professor at King's College London, spoke in an interview with NHK. He played a leading role in Britain's intelligence community for nearly four decades and was a senior official at the Ministry of Defence until 2020.

Rimmer said the UK's information disclosure helped to counter Russia's "false flag" attempts.

He said, "By putting that information out first, it undermined the Russian position. It probably wrong-footed the Russians a bit."

Rimmer pointed out the United States and Britain have a very close intelligence-sharing relationship going back many decades.

He said Britain cannot have a "normal relationship" with Russia, referring to the 2006 murder of a former Russian agent living in exile in the UK after criticizing President Vladimir Putin and the attempted assassination of another former Russian agent in Britain in 2018.

On the future of the Putin administration, Rimmer said that to hope Putin will be "overthrown tomorrow" is "probably wishful thinking." He said the president may claim victory in the war.

Rimmer noted sanctions "always take time to have real impact," saying their effect in six months or a year can only be guessed at.