Although a castle was first erected at Tattershall in the early 13th century, it probably amounted to little more than a fortified stone house. But when it passed to Lord Cromwell in the 15th century, he transformed the insignificant remains to provide an extremely comfortable residence, and a place where he could entertain guests in a manner that befitted his important office. Today, the huge red-brick tower that survives is an imposing reminder of Lord Cromwell's power and wealth.
At the time of Tattershall Castle's grand rebuilding programme, brick had become more fashionable than stone and Cromwell had nearly one million bricks made from the local clay to complete his project. The five-storey rectangular tower with octagonal corner turrets contained a magnificent suite of apartments for Cromwell's personal use. Now marooned as a single unit, the tower was originally adjoined to the main residential buildings of Tattershall Castle, and surrounded by service ranges. Virtually none of these other buildings have survived to any extent, with the exception of the small guardhouse at the modern entrance. To the south of the Great Tower at the edge of the inner moat, the brick foundations to the fifteenth kitchens are still in situ, and a ruinous building in the outer ward probably served as stables. An arrangement of bridges and small gatehouses were placed around the outer and inner moats, and fragments of some of these structures are still visible.
At first glance, the 80ft (24.2m) high Great Tower of Tattershall Castle looks formidable and quite impossible to penetrate should it come under attack. Despite the thickness of the walls, a closer look at the building reveals that many of the 'defensive' features were, in fact, incorporated only to embellish the fašade. Large arched windows with beautiful tracery run round all sides of the tower, from top to bottom, allowing plenty of light into the lofty rooms but providing little in the way of protection. Inside the rooms are laid out in a uniform fashion on each floor, one large central area or hall with smaller rooms located in three of the corner turrets, and a spiral staircase in the other turret. Each main area had a great fireplace, and all four of these have now been restored and returned to Tattershall Castle through Lord Curzon's efforts in the early 20th century.
Looking at the wonderfully preserved state of the Great Tower today, it is difficult to imagine the sight that beheld Lord Curzon when he decided to purchase Tattershall Castle in 1911. After Cromwell's death, Tattershall Castle had been stripped of valuables and it is doubtful whether it was lived in again until it fell into Crown possession. From the last quarter of the 16th century until the end of the 17th century, Tattershall Castle was owned by the Earls of Lincoln. For the next 200 years it was left abandoned, and at the mercy of the elements. With most of Tattershall Castle having been demolished already, there was a real danger that the tower's days were also numbered. Thankfully, Lord Curzon recognised its historical worth, and visitors today are still able to enjoy some of the former splendour of Cromwell's great Lincolnshire masterpiece.