Pinsent Masons has been appointed by the Government of Russia's Samara Region to represent it at the UK High Court in its efforts to recover almost RUB1bn (£20m) from oligarch Boris Berezovsky.

The UK firm won the role after a tender process that was sparked by the Samara Region filing action to recover RUB989m (£19.4m) it claims it is owed by Berezovsky.

According to Russian law, the appointment is subject to a ten-day appeal window which will close on 29 November.

The long-running case dates back to the mid-1990s, when Berezovsky (pictured) was the head of Russian company LogoVaz. The oligarch is alleged to have defrauded the administration of the Samara Region of billions of roubles.

Although some of the debt has been recovered, the Government of Samara is now stepping up efforts to recoup the remaining £19.4m it claims is still outstanding.

Berezovsky was recently successful in gaining a first instance ruling preventing Aeroflot Russian Airlines pursuing a Russian obtained judgment in an English court. Aeroflot is considering its position on appeal.

Pinsents' litigation partner Michael Fenn, who worked on the Aeroflot case, is understood to be lined up to represent the Samara region alongside fellow litigation partner Yuri Botiuk.

Addleshaw Goddard litigation partners Mark Hastings and John Kelleher, who also worked on the Aeroflot case, would be expected to continue to work with long-term client Berezovsky should a claim be served.

Pinsents declined to comment.