The giant aldabra tortoise died in Calcutta Zoo of liver failure, taking all the secrets of an existence spanning three centuries with him.
"Historical records show he was a pet of British general Robert Clive of the East India Company and had spent several years in his sprawling estate before he was brought to the zoo about 130 years ago," said Jogesh Barman, the West Bengal forest minister.
"We have documents to prove that he was more than 150 years old, but we have pieced together other evidence, like statements from authentic sources and it seems he is more than 250 years old."
Details about the tortoise's early life showed that British sailors had brought him from the Seychelles and presented him to Clive, who was rising fast in the East India Company's military hierarchy, the minister said.
If Adwaitya's age is proved by planned carbon-dating of his shell, he will take the longest-lived crown from another tortoise with connections to empire.
Tui Malila, who was presented to the Tongan royal family by Captain Cook, in either 1773 or 1777, remained in their care until its death from natural causes in 1965. This means Tui Malila was at least either 188 or 192 years old.
Some believe Adwaitya's link to Clive of India to be a romanticisation. "It's rather thrilling to imagine that this ancient creature once belonged to someone as renowned as Clive, but there's little historical evidence to back this," said Bunny Gupta, a Calcutta historian.
She said it was possible that Adwaitya - whose name means The One and Only - was owned by the Ezras, a wealthy Jewish trading family who lived in lived in Calcutta from the 18th century. The Ezras were known for their philanthropy and interest in zoological matters.
When Calcutta Zoo was opened they donated several animals and there is still an enclosure named after them.
As befits his size and age, Adwaitya treated his admirers with benign aloofness.
Most of the time they would see him sitting in front of his favourite platter of vegetables and wheat bran, chewing on a choice titbit in a meditative fashion.
But for the last week or so he had been ailing and even his favourite greens did not seem to interest him much.
For Adwaitya's fans his demise is upsetting. "This is a sad day for us. We will miss him very much," a zoo keeper said.
One regular visitor said: "His was the first enclosure that we would go to when we came to the zoo. It was like paying our respects to the most venerable of creatures before going on to see the others."
Another woman said: "Thursday is a school holiday for my daughter and visiting the zoo on this day was a must."
She added: "Today, it's Thursday and we're at the zoo, but it's heartbreaking to see Adwaitya's empty cage. In fact, my daughter broke into tears as soon as she saw the cage."
Flawed hero who took his own life
ROBERT Clive, the son of a Shropshire squire, is credited by many as the general who consolidated the British Empire. He became a military ensign in 1744 and later was known as the victor of the Battle of Plassey in June 1757 when he defeated the Nawab of Bengal, a triumph that signalled Britain's control over India.
He became the first governor of the Bengal Presidency as a reward. His victories over the Dutch at Biderra (1759) consolidated the British position as the dominant European power in the sub- continent.
But later, accused of financial irregularities, Clive, who had a history of trying to take his own life, committed suicide in November 1774.