Crow was 52 years old.
The Evening Standard's chief news correspondent is claiming he suffered a heart attack.
Tributes have been paid to him.
Crow was interviewed on Radio 4's PM last night:
In the interview he was taken to a restaurant in Westminster where he drank red wine and ate hake with treacle tart. He explained some of his beliefs:
On ideology: "I'm a communist-socialist. A society based on need rather than greed. It's rights and wrongs really."
On his behaviour: "At the end of the day, to be general secretary of union, you've got to be larger than life. You wouldn't want to walk around in a grey suit and eat a cheese sandwich. Or do you want someone who's got a bit of spark about them?"
On his high wages: "I'm worth it. Our members in the main have had pay rises every year all the way through austerity, they've got good pensions, they've got good holidays - they could be better."
On MPs' pay: "I do believe MPs should have a pay rise. Some people believe they should live in a tent. I want my MP to have decent accomodation. I want them to have a proper meal."