In particular he has spent decades following the fortunes of India's tiger population.

His stewardship of the Ranthambore Foundation was recognised and he was appointed a member of the Tiger Task Force of 2005 by the Government of India. When it was time to finalise the report of the Task Force, Mr.Thapar expressed his strong dissent at the overall approach of the high power body. He criticised the majority Task Force view in his dissent note as excessively focussed on the prospects of co-existence of tigers and humans, which was, in his view not consistent with the objective of the panel. The Task Force has paid inadequate attention to the biggest questions that face tiger conservation today, such as poaching, absence of science and hurdles to research posed by bureaucracies.

Mr.Thapar's writings have analysed the perceived failure of Project Tiger, a conservation apparatus created in 1973 by the Government of India and its nature-loving Prime Minister Indira Gandhi. He has critiqued Project Tiger, drawing attention to its mismanagement by a forest bureaucracy that is largely not scientifically trained. His most recent book The Last Tiger, Oxford University Press makes this case strongly.

Among the consistent criticisms levelled by Mr.Thapar at India's Ministry of Environment and Forests relates to its unwillingness to curb poaching through armed patrols and its refusal to open forests to scholarly scientific enquiry.

His famous relationship with 'Macchli' a female tigress is documented in some of his chronicles.

His father Romesh Thapar was a highly respected journalist and political commentator. The veteran journalist, Karan Thapar is his cousin and Romila Thapar is his aunt. Pran Nath Thapar fifth Chief of Army Staff of the Indian army was his great uncle.

He is married to theatre personality and actress, Sanjana Kapoor, daughter of Shashi Kapoor, and the couple have a son, and lives in Delhi.