Not only was the castle built at considerable expense, but it was built relatively rapidly; construction of large stone castles often took the better part of a decade; for instance the work at Dover Castle took place between 1179 and 1191 (at a cost of £7,000). Richard was present during part of the construction to ensure construction proceeded at a rate he was happy with. According to William of Newburgh, in May 1198 Richard and the labourers working on the castle were drenched in a "rain of blood". While some of his advisers thought the rain was an evil omen, Richard was undeterred: