Actor Ranveer Singh has said that the upcoming film 'Padmavati' is his biggest challenge as an actor. Ranveer will be portraying 'Alauddin Khilji', the medieval-era Delhi ruler, who fell in love with queen 'Padmavati', played by Deepika Padukone. "It's very difficult. It's physically, emotionally, mentally very draining... I prepared very hard for it, almost a month," added Ranveer.