Mistry recently warned Tata's European steel business faced potential writedowns of more than $10 billion, only some of which have been booked, according to an Oct. 25 e-mail the ousted chief sent to the board of holding company Tata Sons Ltd. Mistry told Tata Sons directors multiple times of problems in group companies including Tata Steel, Tata Teleservices Ltd. and Tata Motors Ltd., the owner of Jaguar and Land Rover, according to the person. A strategy document presented by Mistry in September gave details of ways to fix the problems in the companies and the key risks to the group, the person said. The deliberations at the tea-to-software giant help shed light on the power struggle behind India's most dramatic boardroom coup in years.