"I first met Om when we worked on a film together in Canada called The Burning Season in 1993," Ayub said.
East is East was evolving in Ayub's mind as an autobiographical play based on his experiences of growing up in Salford, near Manchester, in the 1970s, with his eight brothers and one sister. His father, an immigrant from Pakistan who had married an Englishwoman, was determined his children should grow up to be "good Muslims".
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For millions of people in the UK and across the world to some extent, it was the role that define Om, who died on Friday in Mumbai, aged 66.
He was one of probably only three actors from India who found acceptance in the UK, the two others being Roshan Seth and the late Saeed Jaffrey. But while they could affect clipped English accents, Om's style was altogether earthier.
In the early 1990s, " East is East was still in a bottom drawer but even then I thought he'd make a wonderful George", recalled Ayub.
East is East first opened as a play in 1996 at the Birmingham Rep. It has turned to be one of the most successful plays to be staged in Britain in the last 50 years.
It was seen by a producer, Leslee Udwin, who immediately snapped up the film rights. When she was considering who to cast in the crucial role of George Khan, "it was Ayub who said: 'I know someone who would be perfect,'" Leslee said.
The role was a complex one and called for someone capable of doing comedy but who could also play an unbending father isolated from his children.
"Very few people have that kind of acting ability," observed Leslee, who found herself plunged into controversy in India in 2015 when she directed India's Daughter. It was a documentary based on the 2012 fatal rape of a medical intern in Delhi.
"In a quiet way, Om helped me," revealed Leslee.
In 2010, she made a sequel, West is West, which sees George Khan returning to his native village in Pakistan. Leslee has had in mind a trilogy - "and of course I am devastated. I also won't be able to make the trilogy with Om."
Ayub said: "How lucky I was to find such an amazing collaborator for the films of East is East and West is West. It's rare when an actor comes along and lifts a character from the page and takes it on to dizzying heights. That is what Om-ji did for me when he played George Khan."
"It was an honour to work with him and I'm truly saddened I won't be able to write for him again," Ayub said. "His passing is a tremendous loss to the film industry - East and West."
The late Jagmohan Mundhra cast Om as a hardline cleric in Shoot on Sight in 2007, and he also acted opposite Helen Mirren in The Hundred-Foot Journey in 2014. Based on the book by Richard C. Morais, the story is of a man who opens a curry house in a village in France opposite a Michelin-star restaurant and the conflict that erupts and the subsequent harmonious resolution.
Om looked completely at ease when he joined Mirren at a promotional media conference in London.
He was cast in Sangeeta Datta's Life Goes On along with Sharmila Tagore and Girish Karnad in 2009.
"I am shattered with the news of Om-da's passing," said Sangeeta. "He was one of the bastions of the Indian film industry and perhaps the most significant Indian actor who featured in international productions.
"Om Puri was a leading face of the parallel cinema movement. I have known him for more than 25 years, from my early days in the film industry. We worked on Basu Bhattacharya's Aastha. More recently, it was a privilege directing him in Life Goes On. To see him prepare for his role, his method, his timing, were all inspirational lessons for the rest of the cast," Sangeeta said.
"We have not only lost a great artist, a pioneer of New Wave cinema but also one of the most talented, genuine, loving people I have known in my life," she added.
A "saddened" Sharmila said: "He was fun to work with. He was a thorough professional, a good actor with perfect timing."
-The Telegraph, Calcutta