Top political stories right now
Tributes have been paid from across the political divide to RMT general secretary Bob Crow, who has died from a heart attack at the age of 52.
An RMT statement confirmed that Mr Crow passed away in the early hours of this morning.
It added: "The union’s offices will be closed for the rest of the day and the union will make further announcements in due course."
Mr Crow reportedly suffered an aneurysm and massive heart attack, and died at Whipps Cross Hospital in Leytonstone.
Mayor of London Boris Johnson said: "Bob Crow was a fighter and a man of character. Whatever our political differences, and there were many, this is tragic news.
"Bob fought tirelessly for his beliefs and for his members. There can be absolutely no doubt that he played a big part in the success of the Tube."
Former Mayor of London Ken Livingstone said: "He fought really hard for his members. When you look at it, basically about the only working class people that have still got well-paid jobs in London are his members.
"Everybody else has seen their wages and conditions and pensions eroded, he fought [for them] and he kept them, that's why his members kept electing him, he looked after them."
Transport Secretary Patrick McLoughlin offered his condolences to the family of Mr Crow.
He added: "I met him on particularly one occasion when he came to the department to talk to me along with all the other rail union leaders and he was always very straight in his dealings.
"The truth is that we may have disagreed on certain aspects of what he would have liked to have seen happen to the railways but I think both of us wanted to see the overall benefits of the railways and recognise a very important role they can play and in certain areas he was a supporter of some of the things we were doing in investment terms."
The Labour MP Tom Watson tweeted: "Death of a fighter. RIP Bob Crow."
Also on Twitter, the Respect MP George Galloway stated: "Bob Crow was a working class hero. That's something to be."
Paul Kenny, general secretary of the GMB union, told BBC News Mr Crow thrived off the emotive reaction to his industrial action.
Mr Kenny said: "He would laugh at that sort of emotive reaction: in some ways he prayed on it. He realised that people couldn’t match him for argument. He was a fierce debater; he’d come up through the ranks, this was not a boy who’d had a silver spoon put in his mouth at some college."
On The Way Up
Today in Transport
Today in Health and Social Services
Today in Foreign affairs & defence
Today in Party Politics & Reform
Today in Domestic Affairs
Today in Economy & Employment
News, gossip and insight from PoliticsHome Editor Paul Waugh
This morning's top ten must-reads
Today's Five at Five
Find out more about the professional political news service
Bits and bobs from the political day
Hand picked politics - Live
Twitter 17:20 | The Man-Legend that is Simon Burns is now on his feet...#CareBillJamie Reed
Blog 16:58 | Bob Crow: Never one to dodge contentious questionsBBC
Twitter 16:58 | Lloyds - who paid Antonio Horta Osorio a pension top-up of £568,000 in 2013 - is to freeze pensionable pay for its other workers from AprilSteve Hawkes
Twitter 16:55 | Today I'll vote against #Clause119 of Care Bill. It gives Jeremy Hunt powers to close hospitals despite local opposition #saveourhospitalsEmily Thornberry
Blog 16:50 | The coalition can't ignore the fall in sexual and domestic violence prosecutionsThe Staggers
Blog 16:33 | A final chance to defeat the hospital closure clauseLeft Foot Forward
Twitter 16:32 | Health Minister, Dan Poulter, confirms no discussions taking place with other NHS Trusts under the admin proposals for failing hospitalsMargot James
Twitter 16:25 | The list of those Russian officials facing EU sanctions unlikley to be in "hundreds"Norman Smith
Twitter 16:07 | Hearing Paul Burstow make the case for his NC16 amendment to the Care BillZac Goldsmith
Twitter 15:55 | No 10 say PM never met #BobCrowNorman Smith
Latest opinion research and analysis
Most read around the web
Most read on PoliticsHome
Click to see todays front pages and political bits
The political diary