Amitabh still the big boss at 74!

Bollywood megastar Amitabh Bachchan turns 74 next month but he says he’s still hungry for new challenges after his latest movie about sexual violence against women left him deeply moved.

In an interview at his sumptuous Mumbai office, the Hindi film legend of almost half a century said courtroom drama "Pink", to be released on September 16, would challenge attitudes in conservative India.

"During the course of the film there will be substance that will talk about women, society and how morality views them," Bachchan said of the thriller set in India’s capital.

"Delhi has been chosen deliberately as many of these cases have been occurring in Delhi," he added, a reference to several high-profile attacks that have shone a global spotlight on frightening levels of violence against women in India. Rape and sexual assault occur regularly, with incidents hitting the headlines on an almost daily basis, despite tough new laws following the fatal gang-rape of a Delhi student in December 2012.

"Pink", which sees Bachchan play an ageing lawyer with bipolar disorder, centres on three women in their 20s who are molested one night by a group of drunk, socially influential men.

However, it’s the women who end up on trial. A short trailer released by the production company shows one of them being accused of defamation and another of soliciting while a policeman appears unsympathetic to their plight.

"It was a very emotional experience having to enact the circumstances that women go through, what they feel or how society should look at them," said Bachchan, wearing a lime green Nehru jacket.

The actor affectionately known as "Big B", a reference to his decades-long command over Bollywood as well as his six foot one inch frame, was so moved that he penned an open letter to his two granddaughters this week.

In it he urged them and all of India’s granddaughters to make their own choices and "don’t let anyone make you believe the length of your skirt is a measure of your character".

His experiences shooting "Pink", which is directed by Aniruddha Roy Chowdhury, "became a source of inspiration to write that letter", Bachchan explained to AFP in his famous, deep baritone voice.

The 73-year-old, whose birthday on October 11 will see hoards of fans gather outside his home, shot to stardom in the early 1970s on the back of powerful roles in hits "Zanjeer" and "Sholay".