Ben Nevis the summit only to find "fragments of earthen and glass ware, chicken bones, corks, and bits of paper". It was not until 1847 that Ben Nevis was confirmed by the Ordnance Survey as the highest mountain in Britain and Ireland, ahead of its rival Ben Macdhui. The summit observatory was built in the summer of 1883, and would remain in operation for 21 years. The first path to the summit was built at the same time as the observatory and was designed to allow ponies to carry up supplies, with a maximum gradient of one in five. The opening of
Lists of mountains and hills in the British Isles high (also called elevation). The UK government defines "mountain" as land over for the purposes of freedom of access. When Calf Top in Cumbria, was re-surveyed 2016 and confirmed to be almost exactly 2,000 ft, 6 millimetres above the 609.6 m threshold for a 2,000 ft peak, the Ordnance Survey described Calf Top as England's "last mountain". In addition, all British Isles definitions, with the exception of definitions that rely on , include a minimum topographical prominence requirement (also called relative height, or drop, or re-ascent, between neighbouring peaks), which is typically . The lowest minimum prominence is , the