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Photo: MortimerCat, CC BY-SA 3.0 via Wikimedia Commons
It is the remains of a former Grammar School for church choristers that was built by Lord Ralph Cromwell who was also responsible for nearby Tattershall Castle. Accessible at any reasonable time.
Tattershall College was a grammar school in Tattershall, Lincolnshire. The college was established in 1439 and the building that still stands today was constructed between 1454 and 1460. This building was built by the 3rd Baron Cromwell for the education of the church choristers and was once a splendid example of the perpendicular style of Gothic architecture.
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It is an early 15th-century red brick-built castle by the then Lord Treasurer of England Ralph Cromwell. Is set in grounds which include original the original guardhouse, moats and the largest parish church in the country. Open every day except Wednesday from March–October, open at weekends in November and December.