Mumbai, 9 November, 2019: Fifty years ago, on November 7, 1969, a gangly, too tall actor appeared on the big screen in the under-appreciated "Saat Hindustani". It was cinema history in the making but nobody really knew it until many years later. 

Half a century later, Khwaja Ahmed Abbas' film is watched and critiqued again and again as the debut of Amitabh Bachchan, arguably Indian cinema's biggest star and perhaps its most talented actor.

As he completed his golden jubilee in Hindi cinema on Thursday, it was time to unspool a body of work -- astonishing in its range -- that closely mirrors the many twists and turns in India's passage of time. 

Beginning from the socialist "Saath Hindustani" and going up to "Badla" this year, the indefatigable 77-year-old has refused to hang up his boots, making us laugh and cry, dance and introspect with his almost 200 films, some slice of life, some goofy, some memorable and some plain forgettable. 

If a book on the history of Hindi cinema is written, Bachchan will have a chapter all his own as the rare showbiz persona who continues to be relevant with his work even now and has grown to become an important voice in India's civil society with his social media posts, his ad campaigns and charities. 

According to biographer-film historian Yasser Usman, Bachchan's quality to adapt and learn and make everything believable has been a driving factor in the long-standing career of the actor. 

Some of his roles, in Manmohan Desai and Prakash Mehra films for instance, were "too filmy" but he made them credible and believable, he said.

"He never shied away from negative roles or character roles. The grace he injects into each of his roles is commendable. And yes, he is the most punctual star ever," Usman told PTI.

"Zanjeer" was his breakout performance, giving birth to the angry young man Vijay who we saw in various avatars through the decades. He was also the intense Dr Bhaskar Banerjee of "Anand", the fun Anthony of "Amar, Akbar, Anthony", the brooding lover Shekhar of "Mili" and the rich, misunderstood alcoholic of "Sharaabi". 

"Zanjeer" was the beginning of the 'angry young man' persona that became Bachchan's screen identity and a lifelong adjective, reflecting the angst of the urban Indian youth tackling unemployment, corruption and crime.

Middle-of-the-road films with Hrishikesh Mukherjee like "Abhimaan", "Mili", and "Namak Haram" gave him the opportunity to tap into a reality of being a human --insecure, depressed and entitled, respectively.

Films such as "Chupke Chupke", "Namak Halal", "Amar Akbar Anthony" and "Satte Pe Satta" showcased his comic timing. 

Bachchan suffered a near-fatal accident on the sets of "Coolie" on August 2 in 1982. The actor suffers health complications from it even today and calls his recovery a "second birth".

In 1990, Bachchan played the iconic role of gangster Vijay Deenanath Chauhan in Mukul S Anand's "Agneepath". The film was not a success but earned the actor his first National Film Award.

Still trying to play the hero, he soon stagnated with a series of forgettable movies. Remember "Lal Badshah" and "Aaj ka Arjun". 

He attempted to get into filmmaking with his production company Amitabh Bachchan Corporation Limited (ABCL) . Bachchan ended up suffering huge financial losses and went through a career slowdown.

Then the screen man grew up -- literally -- graduating to father roles with the salt and pepper beard and hair.

In 2000, he famously reached out to frequent collaborator Yash Chopra and "asked" for work during bankruptcy. "Mohabbatein" was a turnaround in a sense, helping him in the kind of roles that he continues in till today. 

He also morphed into a star of the small screen with game show "Kaun Banega Crorepati" in early 2000. The show is going strong along with Bachchan, who is currently hosting its 11th season.

The veteran star earned three more Best Actor National Film Awards in the last two decades in starkly different roles in "Black", "Paa" and "Piku".

Film historian S M M Ausaja quotes the late Manmohan Desai who described Bachchan as "one in a million". 

"The best part is that he has always bounced back in all the setbacks that he had... he continues to stay relevant because he has moved with the times. Look at his popularity on Twitter, FB and workwise, and look at the kind of roles he does... ," Ausaja told PTI. 

Usman, too, said Bachchan is an actor of many comebacks, a veteran who has not just survived but also reigned over the industry for five decades.

The untiring Bachchan will next be seen in "Gulabo Sitabo", "Brahmastra", "Chehre" and "Jhund".