Airtel-parent Bharti Enterprises will acquire a 24.5% stake in Britain's largest telecommunications firm BT Group for an estimated $4 billion. The company will buy the shares from telecom tycoon Patrick Drahi-founded Altice UK and will become BT's largest stakeholder. BT was a major shareholder of Bharti Airtel from 1997-2001, when it owned 21% in the Indian telecom giant.