Ireland's Taoiseach, or prime minister, Leo Varadkar, said he wanted to hear Johnson put some "flesh on the bones" over claims he made in his speech outside Downing Street earlier today.

Speaking on state broadcaster RTÉ, Varadkar said the Irish Government is looking forward to working with Johnson on Brexit, bilateral relations and Northern Ireland -- but that confidence and enthusiasm were not a substitute for proper European policy.

One of the sticking points in the Brexit debate is that the UK's departure from the EU could mean the reintroduction of border posts on the frontier between Northern Ireland, which is in the UK, and the Republic of Ireland, which is a EU member. Border infrastructure was often targeted by Irish nationalist paramilitaries during the "Troubles" -- the 40-year sectarian conflict in which more than 3,500 people died.

The current Brexit deal, as it stands, states that neither side can unilaterally leave the backstop, an insurance policy designed to avoid the hard border. The EU has repeatedly ruled out renegotiating the terms of the current withdrawal deal to revisit this agreement.

This has infuriated hard-line Brexiteers, who hate the idea that the EU would hold a power of veto over the UK on that issue, and worry that the UK will never "properly" leave the bloc. They want to be free of the EU customs union, in order to forge international trade deals without the hindrance of European regulations on issues like agriculture, fisheries, food standards and the environment.

"Never mind the backstop, the buck stops here," said Johnson on Wednesday, vowing to take "personal responsibility" for seeing Brexit through.

Varadkar, however, said that a new Brexit deal between Britain and the EU will not happen. "Listening to what he (Johnson) said today, I got the impression that he wasn't just talking about deleting the backstop, he was talking about a whole new deal, a better deal for Britain, that's not going to happen."

Varadkar added that the suggestion that a whole new Brexit deal could be negotiated in weeks or months was "not in the real world."