Harry Leslie Smith, a second world war veteran and anti-poverty activist who described himself as "the world's oldest rebel", has died at the age of 95.
His son John confirmed his death at the Belleville General Hospital in Ontario, Canada.
In a message posted to Harry's Twitter account on Wednesday, John wrote to more than 250,000 followers: "At 3:39 this morning, my dad Harry Leslie Smith died. I am an orphan. #istandwithharry"
Born in 1923, Smith grew up in poverty in northern England and served in the Royal Air Force (RAF) during the second world war.
As a young soldier, he witnessed the floods of refugees across Europe abandoning their homes in the hope of finding safety.
Smith's greatest concern in 2018 was for the millions of refugees today fleeing war, persecution or poverty.
He had been planning to tour Europe's refugee and migrant camps to rally empathy and awareness.
In an interview with Al Jazeera in October last year, he said: "It was such a different world then. Britain was a different country. It was a country with a heart. We have lost some of our early love for each other.
"And today, 'immigrant' is a dirty word, it's ridiculous."
Smith spent his final years writing Don't Let My Past Be Your Future - his fifth book, recording podcasts and giving speeches in support of the welfare state and against neo-liberalism.
A lifelong socialist, he brought the 2014 Labour Party conference to tears with a blistering speech about an England before the NHS, describing "when common diseases trolled our neighbourhoods and snuffed out life like a cold breath on a warm candle flame."
He attracted hundreds of thousands of supporters across the world, using his Twitter feed to comment on current affairs. He was particularly concerned about the recent growth of the far right across Europe.
Jeremy Corbyn, leader of Britain's main opposition Labour Party, was among those who considered Smith a friend.
Smith lost his sister to tuberculosis when she was 10 years old because the family couldn't afford a doctor; his wife Friede, a German who he dearly loved, to cancer, and his 70-year-old son, Peter, to mental illness.
According to his son John, Smith had suffered a fall last week and was in hospital with pneumonia and other illnesses.
He is survived by his sons John and Michael, and two grandchildren.
John had accompanied him for the last eight years on speaking engagements, and had over the past week kept his father's supporters informed of his condition via Twitter.
Tens of thousands of people had sent messages of support to Smith while he was in hospital.
Speaking about the end of his life last October to Al Jazeera, Smith had said: "I had a good life," explaining that he did not fear death.
"I know that once this beautiful life that we don't appreciate ends, it is curtains. There is nothing else."
