Her character will be portrayed at two different ages, with the older one modelled on Waheeda Rehman.

After going back and forth, deciding who his Mehrinissa will be, buzz is that Sudhir Mishra has finally zeroed upon Vidya Balan to play the titular character. Katrina Kaif is now formally out of the race. And Vidya will be joining the team towards the end of the year.

"That's when Vidya will be free of her next assignment namely Rajkumar Gupta's Ghanchakkar," says a source. Interestingly Mehrunissa passed on from UTV to a rival company DAR Motion Pictures.

And Vidya apparently has readily agreed to be part of Mehrunissa. But the priority dates have gone to UTV's Ghanchakkar.

"Sudhir has no option but to shoot with her during year-end when she is free. Since he and producer Nikhil Advani are very keen to have Vidya on board to play Mehrunissa, they are willing to wait it out," says the source.

Vidya will be playing Mehrunissa in two different time zones, at the age of 20 and again at the age of 62. And we hear that Vidya's older role has been modelled on Waheeda Rehman.

Says a source close to the project, "It's interesting that Vidya would be asked to model the older avatar of her character on Waheedaji and share screen space with Bachchan saab and Chintuji. Because Bachchan saab has frequently compared Vidya to Waheedaji."

Vidya will apparently be using some clever makeup and prosthetics to look convincing opposite Big B and Rishi Kapoor. Producer Nikhil Advani refrained from commenting on the actress' presence in Mehrunissa.