I told him that when I write a book, I would write about another side of him and not just historic events or business milestones. I would write about us and our adventures together, and how I saw him, colours and shades of him unknown to the world. Life beyond the great steel wall of 'industry doyen'.

He agreed. 'There cannot be one book that captures everything ... So you do your thing, give your perspective.'

It was their shared empathy for homeless dogs that sparked an unlikely friendship. In 2014, Shantanu Naidu, an automobile design engineer in his early twenties, developed an innovation to save the local strays from being run over by speeding cars. Ratan Tata, himself known for his compassion for stray dogs, took note. Impressed, he not only decided to invest in the venture, but over the years became a mentor, boss and an unexpectedly dear friend to Shantanu.

I Came Upon a Lighthouse is an honest, light-hearted telling of this uncommon bond between a millennial and an octogenarian that gives glimpses of a beloved Indian icon in a warm light.