The tradition of investing the heir of…

The tradition of investing the heir of the monarch of Britain with the title of "Prince of Wales" is usually considered to have begun in 1301, when King Edward I of England, having completed the conquest of Wales, gives the title to his infant heir, Prince Edward (later King Edward II of England).

The Prince of Wales will, from this time, usually be the eldest living son of the King or Queen Regnant of England (subsequently of Great Britain, 1707, and of the United Kingdom, 1801).

The word "living" is important.

Following the death of Prince Arthur, the Prince of Wales, Henry VII will invest his second son, the future Henry VIII, with the title—although only after it was clear that Arthur's wife, Catherine of Aragon, was not pregnant.

The title is not automatic; it merges into the Crown when a prince accedes to the throne, or lapses on his death leaving the sovereign free to re-grant it should another candidate qualify, such as an heir-apparent other than the eldest living son, such as that deceased eldest son's eldest son (for example, George III).