Presented by Peter France from the Banqueting House, Whitehall.
Political life has always been full of mysteries and secrets.
The Zinoviev Letter led to the defeat of the first Labour Government in 1924. Was it genuine - or was it an early attempt to use 'red scare' tactics to bring down a democratically elected government? And if so, who sent it? The Prince of Transylvania received a pension from Charles II and a magnificent burial in Rochester Cathedral. But was he a prince or a con-man - and why was he so hideously murdered?
Christopher Andrew and Gabriel Ronay investigate two political mysteries.