Mumbai: Ratan Tata retired as chairman of Tata Group after a 50-year run on Friday, but kept away from office on his last day at the helm of one of country’s oldest business empires.

Tata, who turned 75 on Friday, is in Pune for his birthday, people familiar with the situation said, adding that there was no clarity on whether he would visit his office later in the day.

Chairman-designate Cyrus Mistry, who made a visit to Bombay House on Friday, will take charge of the new assignment on Saturday, according to people in Tata Sons, the holding company of the group.

Mistry was groomed for the assignment by Tata for a year. The group had earlier announced that he was being appointed chairman with effect from 29 December. Mistry chose the group company Tata Motors Ltd’s entry-level sedan Indigo Manza to travel to work on Friday.

Ratan Tata, who helmed the group for 21 years after being chosen as successor by his uncle JRD Tata, is credited with transforming the group through bold decisions, including large global acquisitions, even as some of its peers struggled to stay relevant after the economic liberalization of the early 1990s.

Mistry, who has been with the group since 2006 in various capacities, hails from the Shapoorji Pallonji family, the largest private shareholder in Tata Sons. Born on 4 July 1968, Mistry graduated with a civil engineering degree from London’s Imperial College of Science, Technology and Medicine and followed it up with a Masters in Management from the London Business School. He was chosen by a five-member panel last year to succeed Tata.

During Tata’s tenure, the group’s revenues grew to around 4.76 trillion in 2011-12 from 10,000 crore in 1991. Tata made some notable acquisitions, starting from Tetley by Tata Tea for $450 million in 2000 to steelmaker Corus by Tata Steel in 2007 for £6.2 billion and the landmark Jaguar Land Rover in 2008 for $2.3 billion by Tata Motors.