Death of a Dissident By Alex Goldfarb & Marina Litvinenko Simon & Schuster, 15.99, 384pp

WHAT is the connection between a Russian tycoon, a Chechen rebel and a former KGB officer poisoned in London? Alex Goldfarb is well placed to know, as a friend and employee of Boris Berezovsky, who went on trial in his absence in Moscow this week. Berezovsky is the billionaire at the centre of the London exiles' group united in their hatred of Vladimir Putin and their opposition to his ruthless submission of the republic of Chechnya. Goldfarb's book, written with the widow of the murdered former agent, Alexander Litvinenko, sheds light on the poisoning by untangling the web that brought them all together.

Marina Litvinenko has only a walk-on part. The real value of Death of a Dissident is to explain the background to the titanic struggle that has pitted Berezovsky against the Russian president since they fell out, after the tycoon helped secure the presidency for Putin in 2000. Goldfarb, a former Soviet dissident, is a man with an agenda. He read out the deathbed statement of Litvinenko, accusing Putin of responsibility for his murder.

But he has written a gripping insider's account of the forces at work in Russia today. It exposes why Putin is right to fear that the Orange Revolution in Ukraine may have provided a blueprint for change in Russia. In Ukraine, Berezovsky quietly channelled more than $40m, allowing the opposition to maintain the street demonstrations that eventually led to the peaceful transfer of power. Goldfarb says that afterwards, his New York-based organisation established an office in Kiev "with an eye towards using it as a bridgehead for a similar peaceful revolution in Russia" .

He sees the Litvinenko murder . . .

and that of the investigative journalist Anna Politkovskaya . . . as part of the "unending contest of wills between Putin and Berezovsky". In their conflict each side, the Kremlin and the "London group", is trying to pin responsibility for murder on the other.

One telling anecdote describes a meeting Berezovsky had with Putin in his FSB office in 1999. The tycoon raised the case of Litvinenko, jailed on trumped-up charges after revealing he had been ordered to assassinate the oligarch. Putin said, "He is a traitor. But I will do what I can."

He then turned the door handle to leave, but it spun uselessly. "F**k, " said Putin. "They can't make the locks work and you want me to run the country."