When at 28, Kumar Mangalam Birla walked into Industry House, the then headquarters of the Aditya Birla group in South Mumbai, to take over as the Chairman of Rs-15,000 crore group, not many in corporate India were enthused.

But the speed at which the young Birla turned around the group into one of India's biggest business houses has turned even his staunchest critic into an admirer.

With Idea Cellular closing India's fourth-largest M&A deal by buying Spice Communications on Wednesday, Birla, 41, has come closer to his dream of breaking into the Fortune 500 list by 2010.

Birla is a tough negotiator and had enough experience behind him to take on BK Modi, the Spice chairman, who had been negotiating with his advisors since last year without results.

The exasperated advisors then had to ask Birla to lead the talks. Birla, a Chartered Accountant and an alumnus of London Business School, has led some of India's biggest M&A negotiations including an acrimonious battle with the Tatas to buy the latter's shares in Idea Cellular.

He also negotiated with the Ambanis to buy Larsen & Toubro (L&T) shares and later with L&T's management to demerge its cement units.

"Kumar Mangalam's working model is completely different from his father's. Kumar Mangalam believes in delegation of power. His style is more group-oriented," says his grandfather, BK Birla.

Kumar now wants a substantial portion of his group's revenues to come from new economy businesses and retail. His group company is rolling out retail stores under the brand name More and with the takeover of Spice, Idea Cellular will have a pan-India presence.

One of the reasons for Birla's success, says his grandfather, is that Birla built a very good Team A. "We had a policy of not recruiting people from outside. He changed it," he says.

He created a new team and put HR systems in place by roping in Santrupt Misra from Hindustan Lever. He hired Bharat Singh in 1996 for Aditya Birla Nuvo, Debu Bhattacharya in 1998 to lead Hindalco, Sanjeev Aga in 1999 for Idea Cellular and Sumant Sinha in 2002 for the retail initiative.

With Birla now setting his sights on the Fortune 500 list, the Aditya Birla group is turning into an institution which corporate India would be proud of.