Simon Sebag Montefiore is an award winning British historian, novelist and television host whose non-fiction works include Jerusalem: The Biography, Stalin: The Court of the Red Tsar and The Romanovs 1613-1918.
His most recent novel, Red Sky at Noon, was the last in a trilogy of Russian-set historical thrillers.
He's just published a new non-fiction work - Written in History: Letters that Changed the World.
Simon talks with Kathryn Ryan about what the letters reveal, and his abiding fascination with Russia.