Cameron Arrives In Russia For Tricky Visit

David Cameron is the first British Prime Minister to visit Russia since the murder in London in 2006 of the former Russian spy Alexander Litvinenko.

Having now landed on Russian soil, it will be a difficult visit.

The primary suspect, Andrei Lugovoi, remains at large in Russia - indeed, he is now a member of the Russian parliament, and the Russians refuse to send him to Britain for trial.

The Litvinenko case has cast a shadow over UK-Russian relations, and will be the elephant in the room during Mr Cameron's talks with President Dmitry Medvedev, and the powerful Russian Prime Minister Vladimir Putin.

Mr Cameron will have to raise it, but then hope to move on to try to improve relations with the Russians which have been gradually improving.

Pressure is being applied to the Prime Minister by four former foreign secretaries.

Margaret Beckett, David Miliband, Sir Malcolm Rifkind and Jack Straw have written a letter to the Sunday Times demanding Mr Cameron push the Russian government on Litvinenko.

They say they also want him to challenge the regime's hostility towards lawyers, journalists and businessmen.

Foreign Secretary William Hague went to Moscow last October for meetings with President Medvedev and Foreign Minister Sergei Lavrov as relations began to thaw, but there is a second problem: Corruption.

Hundreds of British companies operate in Russia, Britain is the sixth largest foreign investor in Russia at close to £20bn, but corruption and bribery remains an obstacle to business.

Mr Hague is travelling with Mr Cameron, heading up a business delegation which includes BP, Britain's biggest private investor in Russia.

But BP's experience in Russia has been little short of a nightmare.

In the latest incident, BP's offices were raided just a day after BP lost out on a multi-billion Arctic exploration deal with Rosneft to American rival ExxonMobil.

Why is Russia economically important, apart from its geo-political significance as a major nuclear power and member of the UN Permanent 5?

Well, not least because Russia is the world's largest oil producer and the largest exporter of gas to Europe (though not to the UK).

The traffic is not all one way: Russia needs British/Western technology and modern management methods, and Moscow has ambitions to become a major financial services centre.

While relations with President Medvedev have improved, the same cannot be said of Vladimir Putin , who is tipped to win the election next March and become, once again, Russia's President.

Pre-Litvinenko, Putin had a reasonable working relationship with Tony Blair, and visited London, but, post-2006, there has been little direct contact, and certainly not at the top level: Gordon Brown apparently only spoke to Mr Putin when Mr Brown became Prime Minister in 2007, a courtesy call - and nothing thereafter.

With the Americans attempting to "reset" their relationship with Moscow, Downing Street says this visit is unlikely to result in any dramatic step forward.

Rather, it's designed to improve relations and communication with the Russian leadership, support UK business in Russia, and deal with the issue of corruption.

But the shadow of Alexander Litvinenko is, once again, likely to overshadow those attempts.