Smith, a former communist, was 'intelligent, articulate and resourceful' and 'a fluent liar' who had 'betrayed the interests of his country for greed'.
Sentencing Smith, 45, of Kingston upon Thames, south-west London, Mr Justice Blofeld said secrets passed 'substantially prejudiced' national security. Smith, perhaps the last of the Cold War spies, was found guilty of three charges. His motives were 'partially ideological, partially financial'.
He was found not guilty of making 'prejudicial' notes at GEC Marconi's Hirst Research Centre in Stanmore, north-west London.
The prosecution claimed Victor Oshchenko, a KGB defector, recruited Smith in the 1970s. He defected days before Smith's arrest, and is now in Britain under diplomatic immunity. He was not called as a witness.
Richard Jefferies, Smith's solicitor, said his client would appeal.Reuse content