Britain's Most Wanted Sunday 25 November 2007 1900 GMT on BBC Two

This World's Mark Franchetti gains unprecedented access to former KGB agent Andrei Lugovoi, the prime suspect in the radioactive poisoning of Russian exile Alexander Litvinenko.

Andrei Lugovoi is wanted for extradition in the UK, yet regarded by many in Russia as a hero.

For the moment Putin has refused to extradite or arrest him, and Lugovoi walks the streets of Moscow as a free man.

He is supported by ordinary Russians, some of whom see him as a loyal patriot.

As he prepares to stand in the Russian parliamentary elections on 2nd December, This World films the moment when Lugovoi announces his political ambitions to stand for the ultranationalist LDPR party.

Lugovoi claims he is driven by a desire to serve the public - but election as an MP would also make him immune from prosecution.

Beneath the surface

Mark Franchetti gets unprecedented access to the former KGB agent

In Russia the truth is often elusive and the real story about who was behind Litvinenko's murder is unlikely ever to come out.

By spending over a month with Lugovoi, reporter Mark Franchetti gets beneath the surface of the man at the heart of the biggest diplomatic crisis between Britain and Russia since the Cold War.

A fascinating portrait of a man who embodies the values of a resurgent Russia emerges, as Franchetti sheds light on the mystery surrounding Litvinenko's murder and asks if Lugovoi is really the killer.