Jeremy Corbyn has appointed the controversial figure and fellow hard-left MP John McDonnell as his shadow chancellor in a move that has disappointed many in the Labour party.
It is a sign that the party's new leader is determined to pursue a radical economic agenda and has dashed hopes that he would use the position to reach out to the wider party by appointing Angela Eagle, who was favoured by many as a less divisive alternative.
Mr Corbyn's past comments and company have been the focus of much media coverage over the last few weeks but Mr McDonnell has an even more contentious past, courting controversy on everything from saying he wanted to "assassinate" Margaret Thatcher to "honouring" members of the IRA.
Here are his four most controversial quotes:
'Assassinating' Margaret Thatcher
When he was campaigning to be Labour leader in 2010 Mr McDonnell joked that he would like to "go back to the 1980s and assassinate Thatcher".
Honouring the IRA
In 2003 he caused uproar by calling for members of the Provisional IRA to be honoured for their role in the armed struggle:
"It's about time we started honouring those people involved in the armed struggle. It was the bombs and bullets and sacrifice made by the likes of Bobby Sands that brought Britain to the negotiating table. The peace we have now is due to the action of the IRA."
He added: "Because of the bravery of the IRA and people like Bobby Sands we now have a peace process."
Nationalise the banks
Shortly before the announcement of his new job on Sunday night, Mr McDonnell told a rally at the annual trade union conference in Brighton that he had been “campaigning for the nationalisation of the banks” for years. “They are jokers, these bankers".
... and the railways and energy firms
This echoed his promise over the summer that a Corbyn government would nationalise industries, such as the railways and energy firms, without giving any compensation.
“Under a Corbyn Labour government this shameful era of governments and ministers colluding in the picking of the taxpayers’ pockets will be brought to an abrupt end," he said.
“Let’s also make it absolutely clear to any speculators in the City looking to make a fast buck at the taxpayers’ expense that if any of these assets are sold by Osborne under their value, a future Corbyn-led Labour government will reserve the right to bring them back into public ownership with either no compensation or with any undervaluation deducted from any compensation for renationalisation.”
'Lynching' a female Tory minister
Labour were involved in a bitter battle to oust former Employment minister Esther McVey at the election - a battle they won - but Mr McDonnell went a stage further when he told an audience during the election campaign: "Why are we sacking her? Why aren't we lynching the b******?".
And his hobbies...?
Well, they include "fermenting [sic] the overthrow of capitalism", according to his Who's Who entry.