Two Russian oligarchs began giving evidence in a court showdown yesterday as part of a battle over a chemicals business.

Alexander Gorbachev, an asylum seeker, is suing sanctioned businessman Andrey Guryev for a return of his claimed share in fertiliser giant PhosAgro.

Should Gorbachev – who is no relation to the former Russian leader – succeed in his court fight, he could end up owning Witanhurst, London’s second largest private house after Buckingham Palace, reports The Telegraph.

The legal wrangle stems from an alleged handshake deal between Guryev and Gorbachev, during which the latter says he was granted a share in a fertiliser business.

That business eventually became PhosAgro – through a series of mergers and consolidations – and for a time even traded on the London Stock Exchange.

Gorbachev was chairman of the larger company until a Russian campaign against another partner in the business, Mikhail Khodorkovsky, prompted him to fleed to the UK.

Gorbachev was eventually granted asylum.

However, he has now claimed that, while living in London, he was offered just $30 million for his share in the business.

He claims he rejected the offer and was then told he had no entitlement to any share, reports the Telegraph.

Gorbachev is now suing in the UK to get back the holdings he alleges were his.

Should be be successful, his representatives believe he would be entitled to the 25-bedroom Witanhurst estate in Highgate, north London, one of Guryev’s few UK assets.

In 2015, The New Yorker first reported Guryev’s ownership of the luxury home. It said there had been a controversial “underground village” – including 70ft swimming pool, cinema, massage rooms, sauna, gym, staff quarters and parking for 25 cars – built under the property.

Guryev is also understood to own a penthouse apartment in Vauxhall, close to the MI6 headquarters.

As he is currently sanctioned in the UK, a High Court judge would have to travel to the United Arab Emirates to take evidence from him.

Both Guryev and Gorbachev have reportedly requested the trial judge, Mr Justice Pelling, appear at the Dubai International Financial Centre as a special examiner to hear evidence from Guryev.

It is understood Guryev will be responsible for paying the costs.

Guryev’s assets beyond his properties have proved difficult to seize. Superyacht Alfa Nero, which the US Office of Foreign Assets Control identified as belonging to Guryev was put up for auction by the government in Antigua and Barbuda after it was reportedly abandoned.

Former Google chief executive Eric Schmidt was reported to have tried buying the yacht for £54 million only to find himself in a complicated legal tussle with Guryev’s daughter, Yulia Gurieva-Motlokhov, who sued saying she was the beneficiary of a trust that owns the vessel.

Gorbachev’s representative was approched for a comment.