Spender: Andrey Goncharenko, a shadowy oligarch, pictured with a companion, has bought and sold mansions in London's most prosperous areas

At £120 million, it is the most expensive town house sold in Britain.

Now a Mail on Sunday investigation can reveal that Hanover Lodge, in exclusive Regent’s Park, has been bought by a shadowy Russian businessman as part of a £250 million shopping spree over three years that has left him with four landmark London properties.

Andrey Goncharenko’s moves in the London property market have been obscured by a series of offshore companies, but, along with the palatial Grade II* listed Regency mansion, he also owns 50 St James Street, Mayfair, which sold for £70million; a mansion in Lyndhurst Road, Hampstead, sold for £41million; and 102 Eaton Square in Belgravia, sold for £15million.

Goncharenko is regarded as an obscure figure even in the secretive world of oligarchs, and the source of his wealth is unclear.

He has never appeared in the Forbes Rich List and his rise to oligarch status has been as shadowy as it was labyrinthine.

However, he has grand plans to spend at least £1.2million gutting the 33,000 sq ft Hanover Lodge, which was renovated at huge expense by its previous owner, Conservative peer Lord Bagri.

Despite being described as ‘humourless’ by one associate, Goncharenko has been spotted on the French Riviera, rubbing shoulders with the Russian elite, and has a reputation as something of a party animal.

In 2011, he was reported by a top social affairs columnist in Russia to have arranged a party at the Le Palm Beach casino in Cannes and flew in performers from The Box nightclub in New York.

In 2012, he was at a charity auction hosted by supermodel Natalia ‘Supernova’ Vodianova, in aid of her Naked Heart Foundation, which aims to build playgrounds for underprivileged children.

At the auction, Goncharenko bought a painting of Supernova herself by US-based artist David Datuna for £460,000. He is yet to settle the bill.

Anastasia Zalogina, president of the foundation, said: ‘I can tell you that so far he has paid 50 per cent of this amount, but he did not refuse to pay the rest. We are in constant touch with him and we are expecting him to pay in full one day. I do not know his reasons for the delay.’

This failure to pay in full is all the more remarkable because in that same year Goncharenko bought Hanover Lodge and 50 St James Street.

The Eaton Square property would appear to have been bought in cash, as Land Registry documents show no mortgage lender.

According to the Russian state news agency RIA Novosti, Goncharenko married a woman called Marina. He is named on company records as a Russian national.

Marina is understood to be active in London’s booming art gallery scene and runs a gallery in Moscow.

A report in society magazine Tatler said Marina ‘prefers to be friends with artists rather than to make money’. Although she did not reveal the identity of her husband, she said: ‘As long as I have a source of money away from the arts field, I will use this [to] support something eternal.’

Grandiose plans: Hanover Lodge, the £120 million Grade II* listed mansion in London's Regent's Park

Palatial: The grand interior of Hanover Lodge features gold walls and chandeliers with floor-to-ceiling windows

Goncharenko’s own interest in art first came to the fore in 2006 when he set up various arts and cultural foundations with Marina, who also set up an arts-focused company in the UK.

Goncharenko’s identity came to light following a dispute between various estate agents over a ‘finder’s fee’ following his Lyndhurst Road purchase.

The tax tribunal, which confirmed the purchase had gone through, revealed that Goncharenko was ‘very annoyed’ after being gazumped on another prime London property.

When he was told the Lyndhurst Road property was available, later that night he drove past and offered to buy it for £43million, according to tribunal papers.

The tribunal heard this was an astonishing offer, ‘considerably in excess of the value of the property’.

With two swimming pools, the double-fronted house boasts seven bedrooms and has been refurbished to the tune of around £10million.

Bought by Goncharenko in 2011 for £41million, it has recently been put back on the market for £46.5million.

In 2012, he bought a £460,000 painting of Russian model Natalia Vodianova but has yet to settle the bill

Equally extraordinary are his grandiose plans for Hanover Lodge. Lord Bagri bought a 150-year lease on the property, built in 1827, from the Crown Estate for £5.9million in 1994 and hired Quinlan Terry, the favourite architect of the Prince of Wales, to transform it into a palatial home.

Goncharenko wants to substantially expand the property, increasing the size of its underground swimming pool, as well as adding a spa, with steam room, sauna, water jets, massage room, gym and yoga room, and a private cinema.

Goncharenko also has expensive plans for 50 St James Street. The building was originally run by fishmonger’s son William Cockford, whose head for figures was matched only by his capacity to fleece the aristocracy.

He ran it as the Crockford’s club and gambling den for 40 years – it is even rumoured to have an escape tunnel.

The grand house then became the louche Devonshire Club for 108 years, until it closed in 1976. It subsequently operated as a casino, before closing in 2009.

Until recently, there were plans for 50 St James Street to revert to its origins as a gentlemen’s members’ club, replete with a spa, 14-bedroom hotel, and two restaurants.

Goncharenko’s origins remain cloaked in mystery but he is understood until recently to have been a senior executive of Gazprom Invest Yug, an offshoot of the controversial Russian oil and gas giant Gazprom.

Lawyers for Goncharenko said he stepped down in 2013.

Respected Moscow business newspaper Kommersant said that Andrey, along with his father Nikolay, owned 83 per cent of a firm called Plamya. Plamya was involved in the building of a huge £1.5billion trading and exhibition centre, Lotus-City, on the outskirts of Moscow, which sold last year for an undisclosed sum, according to the newspaper.

A source told The Mail on Sunday that the deal is likely to have taken the Goncharenkos into the financial big league.

Lawyers for Mr Goncharenko said he had made his money through property development, road haulage and forestry, and had made ‘significant profit’ in the 1990s. He was at Gazprom-Invest YUG between 2002 and 2013.

A spokesman for Gazprom Invest Yug said: ‘According to the current legislation, A N Goncharenko is not obliged to submit a declaration of his income and property because he is not a state official. We do not possess any information if A N Goncharenko owns any property in Great Britain.’

However, documents obtained by The Mail on Sunday confirm Goncharenko’s interests. MCA Shipping (Gib) is listed as the owner of 102 Eaton Square on the Land Registry.

Previous purchases: Built in 1827 and run as a gambling den for the aristocracy with an escape tunnel, there are plans for 50 James Street, which sold for £70 million, to once again become a gentlemen's club

Leafy: Now back on sale at £46.5 million, this double-fronted house in Lyndhurst Road, Hampstead, with two pools and seven bedrooms, has had a £10 million refurbishment after Goncharenko snapped it up

Classical: Built around 1825 by the Grosvenor family and set in London's Belgravia, this Grade II* building is in a classical square where Roman Abramovich also owns property and where Baroness Thatcher lived

MCA Shipping, which is based in Gibraltar, shows Andrey Goncharenko as shareholder. Directors include Redmount Management Services with the company secretary listed as Redmount Corporate Services.

Separate documents reveal that Redmount is linked to Hanover Lodge, 50 St James Street and Lyndhurst Road.

Alex Watzdorf, a top broker who worked on the Hanover Lodge deal, also confirmed Goncharenko bought the house from Lord Bagri.

Following repeated requests from The Mail on Sunday in both the UK and Russia, lawyers for Goncharenko insisted that his property ownership was a private matter and said he was not the registered proprietor of Hanover Lodge, 102 Eaton Square, 50 St James and Lyndhurst Road.

They declined to comment on his failure to pay the balance of the charity painting.