Sinn Fein’s Martin McGuinness has used the rapid motoring time between Belfast and Dublin, 100 miles apart, to illustrate what it means in Ireland when there’s not a hard border.

Following his first full meeting to discuss Brexit as a leader of the Northern Ireland administration with British Prime Minister Theresa May at 10 Downing Street where Scots and Welsh leaders were also present, McGuinness told reporters, “Agreements like the Good Friday Agreement and the St. Andrews Agreement are contingent on there being no obstructions between north and south.

“You can now travel from the center of Belfast to the center of Dublin in almost an hour and a half; you won’t be stopped at a red light or a checkpoint of any description. We want that to continue.”

We should be working to ensure whole of Ireland remains in Europe – @GerryAdamsSF #brexit

— Sinn Féin (@sinnfeinireland) October 26, 2016

May met the leaders of the devolved administrations in Downing Street for two hours on Monday in their first joint conference to hear how the U.K. plans to exit the EU.

Read more: Brexit to push Britain to the margins

First Minister Arlene Foster, who is also the Democratic Unionist Party leader, and Deputy First Minister McGuinness both attended.

Foster said May was very clear and definitive on the issue of a hard border.

“Theresa May had said there would not be a hard border. This is an agreement between her, the Northern Ireland Executive and the Irish government,” Foster said.

May’s bottom line that all the devolved administrations must work together and not “undermine” the negotiations for the U.K. as a whole could present problems.

Scotland and Northern Ireland voted to remain in the EU and Wales and England voted to leave.

Scotland's First Minister Nicola Sturgeon said she was frustrated that more details around the U.K.’s negotiating position were not disclosed during the meeting with May.

Read more: What Brexit will mean for Ireland, Northern Ireland and technology

McGuinness shared her frustration on the lack of information from May at the meeting.

Sturgeon said she is not “bluffing” over her promise to hold an independence referendum if Scotland’s vote against Brexit is “not respected.”

Here's why Scotland and Ireland can't be silenced on Brexit

— Newsweek (@Newsweek) October 26, 2016

BBC assistant political editor Norman Smith said that following Sturgeon’s call for a referendum, May realized what an “awfully big” situation the U.K. faced.

“If she gets it wrong, she risks being the prime minister who took Britain out of the EU but also risks breaking up the United Kingdom,” Smith said.