The kingdom ruled by King Harold and Queen Lillian in Shrek the Third is Far Far Away.
Far Far Away is the principal royal setting of the Shrek franchise. It is presented as a fairy-tale kingdom with a large castle, formal court life, and a population made up of humans and storybook creatures. King Harold and Queen Lillian rule it before Harold’s death, after which Shrek is expected to assume the throne because he is married to Princess Fiona.
Shrek dislikes the idea of becoming king and instead searches for Arthur Pendragon, the next suitable heir. The succession plot drives much of Shrek the Third and makes Far Far Away more than a backdrop: it becomes the political problem Shrek must solve.
Duloc is a different kingdom, ruled by Lord Farquaad in the first film. Worcestershire is associated with the academy attended by Arthur, not with Harold and Lillian’s realm.