Our concept is that as long as the emperor becomes an emperor, then this title is easy to use anywhere within his jurisdiction, but in the West it is different, and the king has a lot of titles on his head, which are of practical use. For example, the title of "Duke of Normandy" on the head of the queen is used in the Channel Islands, while the title of "Duke of Lancaster" is mainly used in the Duchy of Lancaster in the United Kingdom, which is generally suffixed after the title of "Queen".
Some royal children of the United Kingdom, when they are married, the queen will grant them the corresponding titles, such as the identity of "Duke of Cornwall" on Prince Charles, which is the title that the eldest son of the British kings can have; and The title of Prince William is "Duke of Cambridge", and Prince Harry's previous title is "Duke of Sussex". However, most of the current titles in the United Kingdom are honorary titles, and there are no actual fiefs such as fiefdoms, with only a few exceptions.
For example, Prince Charles had the eldest son, the Duke of Cornwall, whose fief was in the Principality of Cornwall, and Charles was nominally the lord of this area, and every year Charles was able to obtain a large amount of related income from the fiefdom of the Duke of Cornwall. The Duchy of Lancaster owns more than 18,000 hectares of land, all of which belong to the British monarch and are not regulated by the Royal Estate Office.
England in the second half of the 15th century
The identity of the "Duke of Lancaster" on the Queen is the same, the Duke of Lancaster is the nominal lord of the Duchy of Lancaster, and the Queen has this title, which is the master of the Duchy of Lancaster. Of course, this seems strange to us, they are already kings, and they have to use additional titles in their own places, just like Ming Chengzu said that he was the emperor of the Ming Dynasty and the "King of Yan".
Some princes in the East will indeed have fiefdoms when they are crown princes, but if they ascend to the throne in the future, these fiefdoms will automatically disappear, but the West is completely different. Some titles, through various means, eventually became the private property that only the monarch could possess, but it was to be taken out alone and could not be mixed with the monarch's title.
The Duchy of Lancaster is one of the two remaining principalities in The United Kingdom, the other being the Duchy of Cornwall, which dates back to the 13th century, when King Henry III of England granted the fief of the Earl of Leicester to his youngest son, Prince Edmund, and crowned him The Earl of Lancaster. Historically, before the introduction of the title of "duke" to Britain, the earl was the highest title in Britain, generally only given to the royal family, such a concept is like the western Zhou Dynasty princely states with the same surname.
Edward III
The title of Count of Lancaster was passed down to the 14th century, and the land he owned was already very vast, and the then Count of Lancaster, Grossmont, was the grandson of Edmund, who was loyal to the king of England at that time, Edward III, so he was also favored, and Edward III raised his earl title as duke. Grossmont's daughter Blanche married back into the royal family and became edward III's daughter-in-law. Edward III's son, Prince John of Gaunt, married Blanche and thus became the heir to the Lancastrian family.
After the death of Edward III, the throne was passed to his grandson Richard II, who was the nephew of John of Gunter, because Richard II was only 10 years old when he succeeded to the throne, so he was regent by John of Gunter, and as a result, Richard II became an adult dissatisfied with his uncle's control of the government, not only exiled his cousin, that is, John's son Henry Boleynbrook, but also confiscated the Lancastrian family's property.
Henri de Bourbon
However, not long after, Henry returned with a horse gun and not only deposed Richard II, but also ascended to the throne himself, which later became Henry IV. From this time on, the Duchy of Lancaster became the private property of the British monarch.
And from the time of Henry IV onwards, the Duke of Lancaster existed only as the private property of the king, not included in the kingdom's property. It was not until the Royal Land Act, passed in England in 1702, that the Duchy of Lancaster belonged to the royal family and the income belonged to the king himself.
Since then, successive British kings have had a separate "Duke of Lancaster", especially since the Victorian era, successive British kings, both men and women, have been called "Lancaster Duke", and there is no "Duchess of Lancaster" or "Lancaster Duchess". Therefore, the current Queen of England is the Duke of Lancaster, and her husband, Prince Philip, has nothing to do with the "Duke of Lancaster".