What is life like inside the Kremlin? And what does the future hold as Putin's presidency nears its end?
The Kremlin is the political heart of the largest country in the world.
For centuries, strong and secretive men have dominated Russia and often terrified the outside world.
But since the collapse of the Soviet Union in 1991, things have been different.
The Kremlin machine has tried to sell Putin to the West as a "liberal democrat", while at the same time selling him to the Russians as the "hard man" their country needs.
In office for the last six years however, in less than two years from now Putin must relinquish the presidency.
And as presidential candidates start to jockey for position, This World discovers what really goes on behind the scenes.
Inside stories
Twenty-three years ago, documentary film maker Richard Denton first went to what was then the Soviet Union, to make a series for the BBC called Comrades.
Now he has returned to film what he could never film before: the people who work within the Kremlin.
From Dimitri Pescov, the president's most urbane spin doctor, to Konstantin Krivorotov, a soldier in the presidential regiment who stands guard over the tomb of the unknown soldier, Denton meets the men and women who work for Putin.
At the time of filming there are scandals in the Russian army and British diplomats are allegedly caught spying.
And all the time, meanwhile, Russians inside and outside the Kremlin walls are beginning to ask the question: after Putin, who will be the next president of Russia?
