The 57-year-old's family revealed the news in a statement to the US magazine People.

The family said the photographer "chose early to keep his journey with ALS private", adding: "Those of us who cared for him did our best to honour his request.

"We are immensely grateful to the tireless doctors who navigated the landscape of this illness with us and to the astounding nurses who became our roommates, often sacrificing their own families to be with ours.

"At this time we ask for privacy to grieve and to come to terms with the impossibility of saying goodbye to Bryan."

ALS, the most common form of motor neurone disease, is a progressive neurodegenerative disease which causes specialist nerve cells in the brain and spinal cord to stop working properly.

It is also known as Lou Gehrig's disease, after the famous New York Yankees baseball player who was forced to retire after developing the condition in 1939.

Those with the illness can have difficulty with walking, speaking, swallowing and breathing.

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Bullock, 59, reportedly first met Randall when he photographed her son Louis's birthday in January 2015.

The Hollywood star won the best actress Oscar in 2010 for The Blind Side and was nominated in 2014 for sci-fi thriller Gravity.

Her breakthrough came with the action thriller Speed in 1994 with her film credits also including 2009's The Proposal, 2000's Miss Congeniality and 2018's Bird Box.