The candidates are asked what qualities they admire in each other.

Of Remain-voting turned Brexiteer Mr Hunt, Mr Johnson says he "greatly admires his ability to change his mind - he supports Brexit now".

Mr Hunt says: "I really admire Boris's ability to answer the question.

"He puts a smile on your face and you forget what the question was."

Mr Hunt says yes, he would support same-sex marriage in Northern Ireland.

Mr Johnson says it is a matter for Northern Ireland.

Will you stop the third runway at Heathrow?

"The bulldozer is a long time off," Mr Johnson says, telling the audience he "retains the gravest of reservations" about it. He once promised to lie down in front of the bulldozers to stop the development.

Mr Hunt says another runway will spread wealth around the country, insisting: "We should back it."

Earlier, the candidates were asked about British-Iranian national Nazanin Zaghari-Ratcliffe who has been imprisoned in Iran over spy charges. Mr Johnson has been strongly criticised for his handling of her case.

The candidates are asked some quickfire questions now.

Should HS2 be abandoned?

Mr Johnson says it should be reviewed.

Mr Hunt says "No", adding that the project will help deal with the north-south divide.

Reality Check

Finding himself under attack over tax, Mr Johnson turns on the format itself.

"This is one of the reasons these blue-on-blue debates are embarrassing," he says, as he and Mr Hunt try to talk over each other.

Mr Johnson is asked by the debate host why his first announcement in the campaign was a tax cut for those on higher incomes.

It was "part of a package" he insists repeatedly.

"It was a mistake," his rival replies, seizing an opportunity to attack. "We are not a party of the rich."

Read more on their tax proposals here.

An audience member asks what the two men will do to help people on lower incomes struggling to make ends meet - she feels they're both prioritising the rich.

Mr Hunt says he recognises his proposed tax cuts for businesses are "not the most popular" but he "wants to boost the economy".

Mr Johnson says his agenda would be to focus on those who are hardest pressed.

He says he wants to raise National Insurance thresholds so people lose less of their wages.

Mr Hunt is asked if the public can trust someone who originally voted Remain?

"Yes," he replies, "because we had that debate three years ago... the question now is who can deliver that decision?"

Mr Hunt says he will keep Sir Kim Darroch - the British diplomat at the centre of the Donald Trump row - until he retires at Christmas.

Mr Johnson says: "Whoever leaked that (the comments on Mr Trump) deserves to be eviscerated."

When pushed on whether he would keep Sir Kim, Mr Johnson doesn't answer directly. His opponent shakes his head in dissatisfaction at that.

Mr Hunt criticises US President Trump's comments on the row over leaked emails from the UK's ambassador to Washington, saying they were wrong.

Mr Johnson says he has a very good relationship with the White House.

"It is very important that we should have a close friendship with the United States, they are our most important ally," he says.

Mr Trump "was dragged into a British political debate I don't necessarily think its the right thing to do as Jeremy said", Mr Johnson says.

He's being pushed hard to go further and directly criticised the president.

Instead, he insists diplomats' comments should not be leaked by ministers.

After a short break, we're back.

The next questioner asks the men what makes each of them the right person for the top job.

Mr Johnson says he has an ability to "get surprising results in difficult situations".

He can unite the Conservative Party and beat Jeremy Corbyn to Number 10 in a general election, he insists.

Mr Hunt says he has won a few elections too.

Part two of the debate is expected to focus on other issues away from Brexit.