Not only is the Cathedral of St. Mungo, or Glasgow Cathedral as it is more commonly known, the oldest surviving building in the city, but it is also the longest-standing house of worship in the Scottish mainland. Founded towards the end of the 12th century, it has seen its fair share of visitors, with an average yearly footfall of around 500,000. Just opposite the Glasgow Necropolis, the city’s sprawling Victorian-era cemetery, an inquisitive investigator may stumble upon a collection of vandalistic inscriptions on the northeastern outside corner of the building. Besides…