Talking about his favourite films, Sabu says: "Though I won a National Award for Thenmaavin Kombathu [directed by Priyadarsan, starring Mohanlal and Shobhana], I will not call it my favourite film. I did not face much of a challenge in that film. My favourite films are those which have been challenging.

"Like Kaala Paani. I put my heart and soul into it. The period in which the story was based [India's freedom struggle] made me work very hard.

"I had to recreate things and places like the Cellular Jail in the Andamans and go into minute details. Recreating the jail was tough. I had to read a lot about that period and brush up my history!

"While shooting in the Andaman Islands, we had to take every item from the mainland, including cars and horses."

In the picture: A train that Sabu Cyril created for Kaala Paani.