Scotland is the first stop on May’s pre-Brexit tour of the four U.K. nations; on Wednesday she will trigger Article 50, beginning the two-year negotiation process of leaving the European Union.

The hour-long meeting between the two leaders took place in a nondescript Crowne Plaza hotel room after May’s office declined to meet in a more secure Scottish government building, according to Sky News. A spokesman for the prime minister said May would underscore where the two leaders agree on elements of Brexit, and tell Sturgeon that the devolved Scottish parliament could regain some powers once the U.K. leaves the EU. In remarks after the meeting, Sturgeon said that May told her the nature of the U.K.’s Brexit deal would be known in 18 months, a timeframe that the first minister says fits with her plans to hold another referendum.

“I think it makes it very difficult for the prime minister to maintain a rational opposition to a referendum in the timescale that I have set out,” Sturgeon said after the meeting on Monday afternoon, adding, “in my view, it was not a question of if but when” the referendum will occur. She plans to formally write to the U.K. government later this week demanding it allow for a second Scottish referendum.

Subscribe to The World’s Most Powerful Women, Fortune’s daily must-read for global businesswomen.

May began Monday’s visit with a speech to the staff of the Department for International Development in East Kilbride, telling them that their work “says that we are a kind and generous country. It says that we are a big country that will never let down—or turn our back on—those in need.” She explained that the coming Brexit process does not mean closing off from the world, but rather taking the “opportunity to forge a more Global Britain.”

May also took the opportunity to reiterate her opposition to Sturgeon’s call for another independence referendum. The first minister’s proposed timeframe for the vote would come in the midst of Brexit negotiations, potentially coinciding with the U.K.’s formal departure from the EU. Westminster’s approval is a prerequisite for any referendum to occur, and May’s position is unlikely to budge.

“Now is the time when we should be pulling together, not hanging apart. Pulling together to make sure we get the best possible deal for the whole of the U.K.,” May said Monday. “Also I think it would be unfair on the people of Scotland to ask them to make a significant decision until all the facts were known, at a point where nobody knows what the situation is going to be.

My position isn’t going to change, which is that now is not the time to be talking about a second independence referendum.”

Sturgeon, the first woman to be appointed leader of the SNP as well as first minister, announced her intention to hold a second referendum on March 13. She said that May’s commitment to a hard Brexit made it “too late to choose a different path in a timely way,” adding that May’s refusal to approve the vote was “tantamount to the U.K. government, having sunk the ship with the Brexit vote, trying to puncture Scotland’s lifeboat as well.”

This piece has been updated to reflect First Minister Sturgeon’s remarks following her meeting with Prime Minister Theresa May.