"Work hard, play hard and sweat a lot at least four times a day," said Prime Minister Narendra Modi today to 700 children gathered at Delhi's Manekshaw auditorium. Millions of more students tuned in from across the country. Mr Modi turned his Teachers' Day address into a cosy chat, as he fielded questions from his audience and narrated anecdotes, admitting that he is "a taskmaster" and favours discipline in the way he works.