Cyrus Mistry was restored as the executive chairman of Tata Sons today by the National Company Law Appellate Tribunal (NCLAT), three years after his dramatic sacking at a board meeting following which Ratan Tata took over as interim chairman. The tribunal said the decision would apply only after four weeks - the time allowed to the Tatas to challenge the order before the Supreme Court. The tribunal held the company's conversion from a public to private as illegal and also struck down the appointment of Natarajan Chandrasekaran as executive chairman of the salt-to-software conglomerate. Cyrus Mistry's abrupt ouster had created an upheaval in the Indian corporate world.