Boris Johnson has warned the Conservative party it is facing extinction if it does not deliver Brexit and put Nigel Farage “back in his box” as he spoke at a hustings of candidates to be the next prime minister from which the press and public were banned. Johnson told MPs from the centrist One Nation wing of the party that it was crucial to take the UK out of the EU at the end of October, arguing that he was the candidate to see off both Farage and Labour’s Jeremy Corbyn. Ruling out calling an early general election or discontinuing parliament to push through a no-deal Brexit, Johnson said: “We are looking at a very difficult situation and we must get ready, eventually, but not immediately, to beat Jeremy Corbyn and put Farage back in his box. We are facing an existential crisis and will not be forgiven if we do not deliver Brexit on 31 October. “I believe I am best placed to lift this party, beat Jeremy Corbyn and excite people about conservatism and Conservative values. We need to realise the depth of the problems we face – unless we get on and do this thing, we will…