It is a question that is not only being asked by the general public, even some of his own MPs – and Shadow Cabinet members – are asking the same thing.
It is not that Corbyn is a newcomer: he has been in Parliament since 1983, sitting as the MP for Islington. But during his time in the House he has been regarded as a radical and he has kept his distance from other Labour MPs. His reputation, however, is well-known, and it is this that has concerned his fellow party members.
Born in Wiltshire (in the west of England), his parents met during the Spanish Civil War, and their political leanings have been passed on to their two sons. His brother is known in the UK as a weather forecaster..
He did not attend university, although he did attend a grammar school. He later started a course at the North London Polytechnic, but after he dropped out he spent the next few years working for trade unions.
After serving for Islington Council, he was elected to Parliament, and in the most recent election he gained a majority of over 60 per cent.
He has been involved in many left-wing causes, including the Stop the War Coalition, the Anti-Apartheid Movement and the Campaign for Nuclear Disarmament.
While an MP, he has maintained a detached approach to his fellow MPs, culminating in the admission of Lucy Powell, whom he appointed as Shadow Education Minister, that she had never met him. Although many of his MPs have little personal knowledge of him, they are all well aware of his political views.
Jeremy Corbyn, 66, is married to Laura Alvarez, his third wife, and is renowned for preferring his bicycle to cars, being vegetarian and having an aversion to alcohol. He has won various awards over the years – one of which was for his beard -- but others recognized his campaigning against apartheid, his support for peace and non-violence..