The fabulously wealthy Hinduja brothers are poised to return to the bosom of respectable British society following the completion of work on their £100 million new home in the heart of London.

Srichand and Gopichand Hinduja, traditionally London-based, have a personal fortune estimated at £6 billion. Like their brothers Prakash and Ashok, they are the descendants of Parmanand Hinduja who created the family fortune by founding an astute trading business between India and Iran.

Although surrounded by a tightly knit group of loyal friends, Srichand and Gopichand have in recent years kept a low profile, ever since it was revealed in 2001 that former Labour minister Peter Mandelson had contacted the Home Office to inquire about one of the brother's application for British citizenship.

The British media's focus on their lives intensified after it subsequently turned out that another Labour minister, Keith Vaz, had made even more energetic inquiries about their passport applications. Questions were also raised about why the Hinduja Foundation had made payments to a company run by Vaz's wife.

Elizabeth Filkin, the UK's Parliamentary commissioner for Standards at the time, conceded that the money had been given for legal advice on immigration issues and that Vaz himself had gained no direct financial benefit, but she was critical of the secrecy surrounding the Vaz-Hinduja connection. She said at the time: "It is clear to me there has been deliberate collusion over many months between Vaz and his wife to conceal this fact and to prevent me from obtaining accurate information about his possible financial relationship with the Hinduja family".

These and other related issues now seem to belong to another age as the Hinduja brothers prepare to move into their four renovated properties on Carlton House Terrace, designed by John Nash and commissioned by King George IV in 1820, where they will be neighbours of the British Foreign Secretary and the Foreign Press Club.

Their new London residence is the Delhi equivalent of moving into a refurbished property on Tughlaq Road or Aurangzeb Road. They are said to have paid some £60 million for the property, which is more than what Lakshmi Mittal, Britain's richest man and also an Indian, paid for his home in Kensington Palace Gardens in another part of London.

At their new home, the Hindujas will be a stone's throw from Trafalgar Square and a short walk from Buckingham Palace. A swimming pool and private cinema are part of the palatial new home which is made up of some 50 rooms over six floors.

But there are other luxurious touches as well, including marble floors, gold leaf and elephant motifs, which prompted a director of English Heritage to comment: "I can't think of another domestic restoration project on this scale with buildings of this importance. Rarely have we seen such opulence allied to such craftsmanship and design."