With Mrs May expected to visit all regions of the United Kingdom during the campaign to sell her Brexit deal before MPs vote on 11 December, the prime minister travelled on to Northern Ireland later on Tuesday.
"Some of our past decisions and actions have left a lot to be desired and I know that they have personally hurt and offended many of our members, voters and the public", she said.
Now their - still separate - encounters with the prime minister at Stormont promise to be rather more consensual than Mrs May's meeting with her semi-detached parliamentary allies in the DUP.
The DUP, a Brexit-supporting, working-class party with strong links to local Protestant churches and a fierce commitment to maintaining Ulster's place in the United Kingdom, is enormously influential in the British legislature at the moment, as Theresa May's minority government relies on their MPs to get legislation through the House of Commons as part of a "confidence and supply" arrangement.
"We will have to see what happens at this time", she said.
Mr Johnson called for a "sensible agreement", but added: "We need to junk the backstop and agree that neither side will introduce a hard border in northern Ireland".
The DUP's arrangement to support the Government on key votes like finance and Brexit matters in exchange for £1 billion extra funding for Northern Ireland is under huge strain due to their dispute over the backstop.
"This is going to be a waste of time today if she doesn't listen to what people have to say to her".
"I really do understand that she is a unionist, that she wants to get the best deal, but actually what this deal does is go against everything she has said around all of that".
Arlene Foster said in Belfast on Saturday that the deal agreed by Prime Minister Theresa May is unacceptable and must be improved upon in the weeks ahead.
Welsh Secretary Alun Cairns, who was travelling with the Prime Minister, said there had been an excellent response to her and her message around the showground.
"We have a working group set up and that is working very well, has met several times and is continuing to work with the USA on this".
Mrs May's Belfast visit comes as US President Donald Trump last night said the withdrawal treaty could hamper trade deals between the United Kingdom and the US - something which Downing Street denied.
The US president also suggested the terms of the settlement would hamper the UK's ability to sign a post-Brexit trade deal with America.
She said the farmers she had spoken to had talked about the importance of getting a deal including a good trade deal with the European Union. "I don't think that will surprise you".
The Chancellor said: "The UK Government is backing these vitally important schools so they can offer a shared education to more children across Northern Ireland".
He said: "It's no use us just brushing that off, saying "No, no, we can do a deal with America"; he's the President of the United States, and if he says it's going to be hard, then it certainly looks like it's going to be hard".
"People here will not be used in the political machinations that are going in Westminster - we need to be protected".
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