The summer house, which was a wooden structure with a thatched roof, was set alight on the grounds of west Fermanagh estate on Thursday at about 8.30pm.A 14-year-old boy and three 15-year-olds were detained. They were released on police bail on Friday pending further enquiries.Florence Court, an 18th-century property, is the former home of the Earls of Enniskillen and is a popular tourist attraction in Co Fermanagh.The summer house was built in 1993 and was a replica of an earlier 18th century building on the same site which had been removed during the 1930s.Jim Chestnutt, the National Trust Manager at Florence Court, said the charity was confident that the building could be restored."Sadly last evening, our Summer House at Florence Court was totally destroyed by fire. Most importantly no-one was injured in the incident. The fire brigade and police attended the scene, and the cause is being investigated."This is a very sad event for National Trust staff and volunteers at the property, and for the thousands of visitors who visit Florence Court annually."The thatched building surrounded with its heather clad walls sat on a high area overlooking the Pleasure Gardens and was a favourite destination for the beautiful views across the gardens to Benaughlin and distant mountains," he added."This news is devastating for the staff and volunteers who love and care for Florence Court, one of our most beautiful places in Northern Ireland. However, as a conservation charity we are committed to looking after these special places forever and the team at Florence Court is confident that the Summer House can be fully restored."Florence Court remains open to the public this weekend, and our team will continue to provide a warm welcome to our visitors."Police are appealing for any witnesses to contact them on the non-emergency number 101.