Queen Elizabeth II spent Wednesday night at a hospital while undergoing “preliminary investigations,” according to a Buckingham palace spokesperson, after abruptly canceling a planned trip to Northern Ireland this week.

The 95-year-old UK monarch entered the hospital on Wednesday and returned to Windsor Castle on Thursday, the spokesperson’s statement read.

“Following medical advice to rest for a few days, The Queen attended hospital on Wednesday afternoon for some preliminary investigations, returning to Windsor Castle at lunchtime today, and remains in good spirits.”

She had been due to attend a church service in the city of Armagh on Thursday marking the centenary of partition and Northern Ireland’s foundation but “reluctantly” accepted medical guidance to cancel the trip, the palace previously said.

She is still expected to attend the COP26 climate conference in Glasgow, Scotland, later this month.