When Mr Cyrus Mistry took over as Tata Group chairman in 2012, little was known about him outside business circles.

In the past four years, Mr Mistry, 48, the younger son of billionaire construction magnate Pallonji Shapoorji Mistry, has managed to stay under the public radar, rarely giving interviews to media.

But his sudden sacking as chairman of Tata Sons, the holding company of the group, has now brought Mr Mistry - who alleged he was reduced to the role of "lameduck chairman" by former chief Ratan Tata - firmly into the limelight.

The Tata Group has in return accused Mr Mistry of "repeated departures from the culture and ethos of the group", but he is no stranger to the group or the Tata family.

His father owns the single largest share in Tata Sons at 18.5 per cent. The senior Mistry vacated his seat on the board for his son, who took over in 2006.

The Mistrys and the Tatas - old business families from Mumbai - have close links as well. Mr Mistry's sister Aloo married Mr Tata's half-brother Noel.

Mr Mistry has described himself as a "voracious reader" who enjoys reading non-fiction and as an avid golfer who has not been able to step on a golf course in the past five years.

Born in Mumbai, he holds Irish citizenship because of his mother, who is Irish of Indian extraction. He graduated with an engineering degree from Imperial College London and has a postgraduate degree from London Business School.

He noted in his letter e-mailed to the Tata board after his dismissal that, under his tenure, the group's operating cash flows had "grown at 31 per cent compounded per annum", improving the balance sheet.

Following his sacking, Mr Mistry has come out swinging, showing that he will not go down without a fight.

But he has yet to reveal his next step even as reports in the media indicate that Mr Tata is looking for a way to buy the senior Mistry's majority stake, which indicates the extent of the fallout between the two business families.

Many believe that Mr Mistry, who is still on the board of many Tata companies, holds the key to how this battle will end and that he has won the first round in the battle with his e-mail.

"It all depends on Mistry, whether he wants to be acrimonious or amicable," said InGovern Research Services founder Shriram Subramanian.

Nirmala Ganapathy