Bereft of friends in Western capitals since its 2014 annexation of Crimea, Russia is celebrating the memory of the British K.G.B. spy Kim Philby, a stalwart supporter who stood by it through thick and thin – and spent the last 25 years of his life in Moscow, often drunk and miserable but still loyal.

Mr. Philby, a notorious double-agent who defected to Moscow in 1963 and died there in 1988, was recently honored with a portrait in a Russian state art gallery and is celebrated in a soon-to-be broadcast film on state television.

The adulation has now reached a new level with the opening of an exhibition in Moscow on the life and work of the best-known of the so-called Cambridge Five Soviet spies in Britain. It portrays Mr. Philby as an unwavering Russian patriot, and it includes the first public display of some of the more than 900 secret British documents he passed on to the K.G.B., the Soviet-era spy agency.