 Complete the following phrase:  The building was originally a small castle on the crest of a ridge on the road inland from the Lincolnshire fen edge towards the Great North Road. It is said to have been begun by Gilbert de Gant, Earl of Lincoln in the early 13th century. However, he was the first and last in this creation of the Earldom of Lincoln and he died in 1156. Gilberts heyday was the peak time of castle building in England, during the 