Who Is the Controversial New Finance Spokesman for Britain's Labour Party?

New British leader of the opposition Jeremy Corbyn's rebellious voting record has been much-discussed in the campaign for the Labour leadership. Indeed he was the most rebellious Labour MP in the last parliament. Except that is, for John McDonnell, the man he has just appointed his would-be chancellor of the exchequer—Britain's equivalent of finance minister, and the second most powerful role in the opposition to the Conservative government of David Cameron.

McDonnell, the chairman of the nine-member Socialist Campaign Group of MPs (which also includes Corbyn), is not a man to mince his words. Combined with a spiky sense of humor, this has led to some highly quotable soundbites, including a 2010 joke about wanting to "go back to the 1980s and assassinate [former British Prime Minister Margaret] Thatcher."

McDonnell himself admits that he is not exactly a uniting figure within the party. On Sunday night, just before his appointment, he told a fringe meeting at a meeting of trade unions, many of whom back the Labour party: "Jeremy's style has been consensual, and what has been appreciated throughout the campaign of the last 12 weeks was to introduce something which hasn't been in British politics for a long while. It is called kindness. It means that you respect one another in a debate even if you disagree. But I am not very good at that. That is why I am not the leader of the Labour Party."

McDonnell is likely to push Labour's strained relations with Britain's financial industry even further, having said as recently as Sunday night that he had been "campaigning for the nationalization of banks for years," before adding, "They are jokers, these bankers." McDonnell will be responsible for putting together a plan to implement "People's Quantitative Easing," a proposal from tax campaigner Richard Murphy that has been adopted by Corbyn, for the Bank of England to electronically "print money" to invest in infrastructure projects.

If there were any question over McDonnell's leftist credentials, one need look no further than his (perhaps tongue-in-cheek) Who's Who entry, where McDonnell lists his pastimes as including "generally fermenting [sic] the overthrow of capitalism." In the run-up to the recent vote over welfare cuts that divided the leadership contenders and led to heated debate on the campaign trail, McDonnell said he would "swim through vomit" to vote against the bill.

However, McDonnell's appointment may have unwittingly strengthened Cameron's hand. McDonnell has made no secret of his feelings toward the role played by the outlawed and now officially disbanded Irish Republican Army during the long conflict in Northern Ireland. In 2003, McDonnell told a gathering to commemorate IRA hunger striker Bobby Sands, who starved himself to death in 1981 demanding privileges for republican prisoners such as wearing their own clothes: "It's about time we started honoring 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."

Northern Ireland's pro-British Democratic Unionist Party, which has eight MPs, is reportedly furious over McDonnell's appointment and could refuse to vote with Labour in the House of Commons, in effect increasing the Conservatives' narrow 12-seat parliamentary majority and making Cameron less vulnerable to rebellions. "It's sending us a message loud and clear and we've heard it," an unnamed party source told the Spectator.

McDonnell has since said he "might not have chosen the right words" about the IRA, saying that he saw himself as having to "go out and sell" the peace process to republicans.

Although establishment Labour figures may be "aghast" at his appointment, McDonnell certainly looks like he'll add some spice to frontline British politics. After all, his predecessor Ed Balls' most famous pronouncement was probably a tweet that simply contained his own name—an event now mockingly celebrated as "Ed Balls day."