Chartered accountant and former Federation of Indian Chambers of Commerce & Industry President RS Lodha is believed to have hundreds of letters from Priyamvada Birla, directing him to protect the assets as well as the identity of the MP Birla group.

Priyamvada Birla also directed Lodha to produce the letters in court if he was required to prove that she was of sound mind and health, while bequeathing the Rs 5,000 crore (Rs 50 billion) worth of assets in her will. The letters are believed to have been written over the last five years, ever since she wrote her will in 1999.

Asked about the letters, a Birla family member confirmed he had been informed about their existence.

"However, we have seen neither the will nor the letters. I cannot comment on their authenticity," he added. RS Lodha was not available for comments.

Lodha had read out the will to the Birlas on Monday but did not hand over a copy of it to them. Legal experts pointed out that had there been no will, Yashovardhan and Priyamvada's sisters would have inherited the group's assets.

If the will is nullified in the law courts, the Hindu succession plan will come into effect. The letters, if they exist, impart a new twist to the controversy over the dispensation of the MP Birla group's assets in favour of Lodha.

Our Kolkata bureau adds: Sources close to the development said Lodha could also produce videotaped evidence to prove that the will was genuine, and that Priyamvada was of sound mind and health when the will was executed.

The Birlas also have marshalled some older documents to support the claim that the property should rightly go to the scions of the Birla family.

Legal experts, however, said the letters and the videotaped evidence would only act as supplementary evidence. The main criteria are the veracity of the signatures in the will and the evidence given by the witnesses.

The Birlas spent the entire day today performing the funeral rites of Priyamvada. Birla Park was barricaded with guards and only specific vehicles and invitees were allowed entry.

Lodha was not present. Offices of the M P Birla group observed minor rituals and served a special meal to all employees in memory of Priyamvada.

Meanwhile, corporate circles were agog with rumours that Rama Prasad Goenka, chairman emeritus of the Rs 6,600 crore (Rs 66 billion) RPG Enterprises, had been approached to resolve the impasse out of court.

Asked about this, Birla family sources said: "The question of  appointing a mediator does not arise at all."

Contacted in Mumbai late in the evening, RP Goenka also denied that he had been approached by either side.