If Jeremy Corbyn wins the Labour leadership in September, as the first public poll of the contest suggests he will, the party will experience the biggest lurch to the left since the days of Michael Foot in the 1980s.
Gone will be Labour's backing of austerity and in will come radical plans to renationalise the railways and utilities, the party would officially support nuclear disarmament, the reunification of Ireland, a radical shift in foreign policy and a radical redistribution of tax.
Scrapping nuclear weapons
Mr Corbyn opposes the £100bn renewal of Britain's trident nuclear system and campaigns across the world for the scrapping of weapons of mass destruction. He is a long-time supporter of the Campaign for Nuclear Disarmament and is on of its three vice-chairs.
He wants to reunite Ireland
Mr Corbyn reiterated his support for a reunified Ireland in a leadership hustings on Sunday. He first met Sinn Fein leader Gerry Adams in London in 1984 and in a demonstration of his continued support of the Irish nationalist cause, he met with republicans Gerry Adams and Martin McGuinness in Parliament as recently as yesterday:
With Jeremy Corbyn & the comrades @ Portcullis House, Westminster. pic.twitter.com/A6Vgmaglsa— Gerry Adams (@GerryAdamsSF) July 21, 2015
Talking to terrorists
He has described terrorist groups such as Hamas as "friends". Asked to explain why, he said: "I think to bring about a peace process you have to talk to people [with whom] you profoundly disagree. There is not going to any peace process unless there are talks involving Israel Hezbollah and Hamas," he told Channel 4 News last week.
Will he advocate talking to Isis?
Scrap tuition fees
Mr Corbyn announced a £10bn plan to scrap tuition fees: £7.1bn would be the cost of providing free university education for all and £3bn would be the cost of reinstating maintenance grants scrapped by George Osborne.
Taxing the rich
He has suggested he would pay for the scrapping of tuition fees through a 7 per cent rise in national insurance contributions for those earning more than £50,000 and a 2.5 per cent hike in corporation tax.
Opposition to austerity
A Labour party under Mr Corbyn would join the SNP in strongly opposing the Government's plans for further cuts and eliminating the deficit. He has predicted five more years of austerity would leave Britain's welfare state unrecognisable. "The gap between the rich and the poor will be bigger than ever," he has said of Mr Osborne's plans for this Parliament.
Labour party policy under Mr Corbyn would support renationalisation in a range of industries, including the state taking back control of the railways and utilities such as gas and electricity.
He has campaigned against privatisation in existing nationalised services, such as the NHS, which he warned will be "largely parcelled up and privatised out, if not destroyed altogether" under five more years of the Tories.
He opposes bombing Syria
He would deal a blow to the Government's hopes of winning a Parliamentary vote to hit Isis targets in Syria by launching air strikes over the country. He is defined by his strong opposition to the Iraq war and has described it as the worst legacy of a Labour government.