On 12 September the Labour Party will elect a new leader. Jeremy Corbyn, a rank outsider just a few weeks ago, is now the hot favourite with the bookies. If he wins, it will be nothing less than a political earthquake. What's the secret of his meteoric rise? And who are the people who have signed up in their thousands to vote for him? With behind-the-scenes access to Jeremy Corbyn, reporter John Ware reveals how, from nowhere, he came to dominate this race. Could a victory for him mean a new dawn for the party, or will it spell electoral oblivion - or even the end of Labour as we know it?