Former deputy prime minister and Labour veteran John Prescott has been admitted to hospital after suffering a stroke, his family has said.
A statement on the 81-year-old's Twitter account said he was taken to Hull Royal Infirmary on Friday.
He is "over the worst" and "talking", former Home Secretary Alan Johnson told the BBC.
Ex-PM Tony Blair said his thoughts were with Lord Prescott, adding: "Hoping very much that he gets better soon."
A statement from the family of Lord Prescott said the hospital staff had been "remarkable and we cannot thank them enough".
"He is receiving excellent care from the NHS," they said, praising the "swift actions" of the paramedics and A&E staff.
Mr Johnson said Lord Prescott was enormously grateful for the care he had received.
"Now it's about the aftercare - it's what comes afterwards that is as important as what happens on the day of the stroke itself," he said.
"They want him to get proper rest to get over this, that's the number one priority, to recover and get over that important after-stage."
He said there had been no concerns for Lords Prescott's health in the days prior to the stroke and there were "no signs of him slowing down at all".
"John is such an important figure now, as he has always been, in the Labour Party and I think there's enormous affection for him well beyond the Labour Party," Mr Johnson said.
"He's a character. Around Hull and East Yorkshire he's hugely respected, but it goes much wider."
A former trade union activist, Lord Prescott entered Parliament in 1970 as Labour MP for Hull East and went on to hold the seat for almost 40 years.
He became a Labour frontbench spokesman in 1979 and joined the shadow cabinet in 1983, with responsibility for transport.
He served as deputy to former Prime Minister Tony Blair for 10 years between 1997 and 2007, and received a peerage in 2010.
'John is John'
At the height of his political career, Lord Prescott was a favourite target of the tabloids, dubbed "Two Jags" - after the two official Jaguar cars he is meant to have had at one point.
He famously punched a man who had thrown an egg at him while on the 2001 general election campaign trail.
"John is John," Mr Blair said the following day, after pictures of the scuffle featured in the press around the world.
In 1993, in what was perhaps his greatest claim to fame, he called for the end to the union block vote and was credited with saving the then Labour leader John Smith from a humiliating defeat.
His role as a power-broker and counsellor smoothed the often strained relationship between Mr Blair and Gordon Brown, and also helped ensure a trouble-free transition from one leader to the other.
He also provided an important link between the New Labour of Mr Blair and Mr Brown and the party's old Labour traditions.
As environment, transport and the regions secretary in 1997, he was a key player in agreeing Kyoto Protocol on climate change - an international agreement setting targets for industrialised countries to cut their greenhouse gas emissions.
In the early 2000s, he proposed an elected regional assembly, but this was rejected in the north-east in a 2004 referendum, with 78% voting against.
After the news broke about Lord Prescott's health, Labour MPs sent him their best wishes.
Leader Jeremy Corbyn said his thoughts were with his "good friend John and his family and friends at this difficult time".Skip Twitter post by @jeremycorbyn Report End of Twitter post by @jeremycorbyn
Shadow chancellor John McDonnell told BBC Politics Live: "I want to send my best wishes to John and my love to all his family.
"I think right across the Labour and trade union movements, even I think a lot of his opponents, will be wishing him a speedy recovery."
Labour MP for Ilford North and member of the Treasury Committee Wes Streeting said: "Wishing John well - and looking forward to him being back in the tea room giving me a ticking off again soon!"
Angela Eagle, MP for Wallasey, said: "My first boss in government - get well soon John."
Anna Turley, MP for Redcar, said: "Sad to hear this - wishing John well."