Why Russia Spies
The Cold War is over.
But some habits die hard.
Since 2007 Russian nuclear bombers have been flying provocatively close to UK airspace, triggering interception by RAF fighters.
The Royal Navy has encountered Russian 'hunter-killer' submarines.
And as the recent discovery of a spy ring in the United States revealed, Russian agents remain active against the West.
With remarkable access to Britain's military and intelligence worlds, Peter Hennessy examines the scale of Russian activity - and what it tells us about the Russia-NATO relationship.
Russian agents remain against the West.
Peter Hennessy investigates why.