BRIDOL is the British Sundial Society's Register of Fixed and Mass Dials, which gives detail and photographs of about 8000 fixed sundials and 3000 mass dials in the UK.
Some of these are in private gardens, but the majority are publicly available.
The circular dial is located above the first floor window on King John’s Tower on the SW corner of the south façade of the castle. It shows hours 5am to 4pm, using IIII and XII, with hour and half-hour lines. The fimbriated lower edge to the triangular gnomon support may portray a man’s face. A decorative surround includes a scallop shell at the top and the date at the bottom.
The dial and its ‘partner’ on the adjacent wall (SRN 7876) are on the oldest part of Grimsthorpe Castle, which dates from 12/13th century (but earlier than King John). The dial was installed in 1757 during the time of the third Duke of Ancaster who inherited in 1742 and was very active. He commissioned Capability Brown to landscape the grounds in 1771. The first Duke had the castle remodelled entirely by John Vanbrough. It is a Grade 1 Listed Building; the listing mentions sundial as dated 1756.
