Private equity major Warburg Pincus on Monday announced that it has acquired a 90 per cent stake in non-bank lender Vistaar Finance for USD 250 million. The stake in the 13-year-old company has been acquired through a combination of primary and secondary investments, the PE major said in an official statement. The acquisition has been done in partnership with banker Avijit Saha, who joins the company as the chief executive, it said.