New Zealanders have spoken about the death of their much admired colleague and friend, world renowned theoretical physicist and author Stephen Hawking.

"He was a role model for us all," said Kiwi screenwriter Anthony McCarten, who wrote The Theory of Everything, the biopic about Hawking's life.

McCarten recalled the last time he saw him, when he delivered a tribute to him from the stage.

"There he was, and that face, often so inert, broke into his big rock-star smile.

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"That is my lasting image of him - a man who despite all the afflictions of his disorder and illness always had a smile on his face."

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Anthony McCarten, who wrote The Theory of Everything recalls his lasting image of Hawking.

In 2004 McCarten boldly knocked on the door of Hawking's first wife Jane Hawking, to ask for the rights to her autobiography Travelling to Infinity. He then went on to write the screenplay to The Theory of Everything.

"Upon watching it, when the lights came up there were tears from [Hawking's] cheeks and he seemed to be very moved by the film. He typed the words into his computer 'broadly true', then he became a great supporter of [the film] - a great joy and quite a relief.

"My first reaction [upon hearing of his death], was if somebody had told him when he was 21 years old that he would live another 55 years, after being given a two-year death sentence by doctors, he would have grabbed it.

"He is free, finally free of that damn wheelchair, breathing apparatus, four-words-a-minute communication, and gone to his rightful place among the stars.

"The final lines of his great book, A Brief History of Time, 'who are we, why are we here – when we understand that we will know the mind of God'. I can only think he got his answer now."

Dr James Fergusson, a New Zealand-born lecturer at The Stephen Hawking Centre for Theoretical Cosmology at the University of Cambridge, said he would be "very sorely missed in the department".

"It feels pretty weird being in today and seeing his door closed - if he was in it was almost always open - and knowing he won't be in again.

"I always felt like I should work a bit harder and try to be a bit smarter to justify being in the same building with him."

At just 10 years of age Fergusson was captivated by Hawking's book A Brief History of Time.

Fergusson understood "almost nothing" but found it fascinating regardless.

He went on to complete a double honours degree in Maths and Physics at University of Otago before setting his sights on studying part III maths at the University of Cambridge in England.

He knew that if he was accepted into the same university as Hawking, he wanted to finally study cosmology.

Hawking attended Fergusson's interview alongside other professors.

"I was feeling pretty nervous when I went to meet him but it began pretty well until I made some joke, which I can't remember, which made him laugh," Fergusson said.

The problem was his new software was quite sensitive to the movement of his cheek and the laughter proved too much for the software which promptly crashed, he said.

"The result was we then had to sit there for 10 minutes while we waited for his nurse to re-boot his chair awkwardly smiling at each other.

"Unsurprisingly, I ended up doing my PhD with someone else in the department, then stayed on to do a couple of post-docs and eventually got my current position as the Centre for Theoretical Cosmology lecturer."

For the past 14 years, while never working directly with Hawking, Fergusson saw him often because their offices stood only a couple of doors apart.

"I used to look after his pot plants when he travelled - I only killed one."

Hawking was brilliant and had a great sense of humour, Fergusson said.

Fergusson recalled an office Christmas party at which Hawking had given his blessing to another colleague to dress up as him in his stead.

The theme was "predictably" set within the science fiction genre and the pair had agreed Hawking had been in more science fiction shows than most actors.

The pretend Hawking had stuck a laptop onto the wheelchair he was sitting in and was chatting animatedly to people at the party while holding a glass of wine.

"Doesn't Stephen look well," Fergusson's wife remarked.

The whole thing said something about Hawking's character, Fergusson said.

Hawking was 76 when he died peacefully yesterday afternoon (NZT) at his home in Cambridge.

At the age of 21, Hawking was diagnosed with a degenerative motor neurone disease similar to amyotrophic lateral sclerosis (ALS) and was told by doctors it would probably kill him within two years.

He was confined to a wheelchair by the time he was 30, and in 1986, aged 44, he was required to have a tracheotomy to save his life after an attack of pneumonia, a procedure that removed what remained of his speech.

Over his lifetime Hawking carved an incredible legacy with his theories on the cosmos.

The Stephen Hawking Medal For Science Communication was established in 2015 to acknowledge those who, like Hawking, were promoting the public awareness of science.

In May last year, Hawking warned that humans should leave earth within 100 years if they wanted to survive.

He believed that life on Earth was at an ever-increasing risk of being wiped out by a disaster, such as asteroid strikes, epidemics, over-population and climate change.