In the early Middle Ages such styles, couched in the second or third person, were uncertain and much more arbitrary, and were more subject to the fancies of secretaries than in later times (Selden, Titles of Honor, part I, Ch. vii. 100). In English usage, the terms Highness, Grace (which is not used exclusively for the sovereign), and Majesty, were all used as honorific styles of Kings and Queens until the time of James I of England. Thus in documents relating to the reign of Henry VIII of England, all three styles are used indiscriminately; an example is the King's judgment against Dr Edward Crome (d. f562), quoted, from the Lord Chamberlains' books, ser. I, p. 791, in Trans. Roy. Hist. Soc. N.S. lOX. 299, where article 15 begins with Also the Kinges Highness hath ordered, 16 with Kinges Majestie, and 17 with Kinges Grace. In the Dedication of the Authorized Version of the Bible of 1611, James I is still styled Majesty and Highness; thus, in the first paragraph, the appearance of Your Majesty, as of the Sun in his strength, instantly dispelled those supposed and surmised mists ... especially when we beheld the government established in Your Highness and Your hopeful Seed, by an undoubted title. It was, however, in James I's reign that Majesty became the official style. It may be noted that Oliver Cromwell, as Lord Protector of the Commonwealth, and his wife, were styled Highness, which is unusual for a republic.
In present usage the following members of the British Royal Family normally have the right to be addressed as Royal Highness (HRH, His or Her Royal Highness): The children of past and present Sovereigns, the grandchildren in the male-line and the eldest son of the eldest son of the Prince of Wales (decree of 31 May 1898). A change of sovereign does not entail the forfeiture of the style of Royal Highness. However, the sovereign has the right to grant or revoke the style of HRH and other titles (e.g., Princess Royal).
As a general rule, the members of the blood royal of an Imperial or Royal house are addressed as Imperial or Royal Highness (French Altesse Imperiale, Altesse Royale; German Kaiserliche Hoheit, Königliche Hoheit; Spanish Alteza Imperial, Alteza Real, etc.) respectively. In Germany, Austria (and other former parts of the Holy Roman Empire) the reigning heads of the Grand Duchies bear the title of Royal Highness (Königliche Hoheit), while other members of the family are simply addressed as Grand Ducal Highness or Highness (Großherzogliche Hoheit or Hoheit). Hoheit is borne by the reigning dukes and the princes and princesses of their families. The style Serene Highness has an antiquity equal to that of highness, and was a title borne by the Byzantine rulers, as were serenitas and serenissimus by the Emperors Honorius and Arcadius. The Doge of Venice was also styled Serenissimus (Latin 'Most Serene'). The crowned republic and the (later Austrian, then Italian) city itself remain widely known as la Serenissima. Selden (op. cit. part II. ch. X. 739) calls this style one of the greatest that can be given "to any Prince that hath not the superior title of King". In modern times Serene Highness (Altesse Sérénissime) is used as the equivalent of the German Durchlaucht, a stronger form of Erlaucht, illustrious, represented in the Latin honorific superillustris- Thackeray's burlesque title Transparency in the fictitious court at Pumpernickel very accurately gives the meaning. The style of Durchlaucht was granted in 1375 by the Emperor Charles IV to the electoral princes (Kurfürsten), the highest rank under the Roman Emperor).
In the 17th century it became the general style borne by the heads of the reigning princely states of the empire (reichsständische Fürsten), as Erlaucht by those of the comital houses (reichsständische Grafen, i.e. Counts of the Empire). In 1825 the Imperial German Diet agreed to grant the style Durchlaucht to the heads of all mediatized princely houses domiciled in Germany or Austria, and it is now customary to use it of the members of those houses. Further, all those who are elevated to the rank of Fürst (prince in the *secondary meaning of that title) are also styled Durchlaucht. In 1829 the style of Erlaucht, which had formerly been borne by the reigning Counts of the empire, was similarly granted to the mediatized countly families (Almanach de Gotha, 1909, 107).
His Highness, often abbreviated HH, is a style for members of ducal families, some grand ducal families, and lesser members of some royal families. The third case is the only usage of the style that is still used officially. However, socially, many formerly-reigning ducal and grand ducal families assume the style HH, but this is only used socially and they are not normally referred to as such in any official capacity.
The style is officially used by junior members of the royal houses of Denmark and the Netherlands. Before 1917, it was also used by some junior members of the British royal house. The style was also once used by the ruling families of the Grand Duchies of Saxe-Weimar-Eisenach, Oldenburg, Mecklenburg-Schwerin, and Mecklenburg-Strelitz, and of the Duchies of Brunswick, Anhalt, Saxe-Coburg and Gotha, Saxe-Meiningen, and Saxe-Altenburg, as well as by the House of Schleswig-Holstein, which never ruled. Surviving members of these families are sometimes known by the style.
Example of official holders of the style Highness:
Examples of other people entitled to the style Highness:
In Samoa the heads of the two paramount chieftain carry the title Highness. Both the current and previous Heads of State were titles High Highness.
In 1876 Queen Victoria of the United Kingdom was amongst the mightiest rulers, but by protocol was accorded precedence below the Austrian, German and Russian Emperors (the 'three eagles'), and in particular would be outranked by her eldest daughter, married to the heir to the less powerful German Empire. This was a consideration for Parliament to raise the Sovereign in precedence by creating the new title of Emperor/Empress of India, in chief of the British crown's position as Paramount ruler of British India, as such the colonial successor to the Mughal dynasty which had the imperial style Padshah-i-Hind. However, the British sense of tradition led to the old royal style in chief of the European UK remaining the lead title, the short formula being King-Emperor, not the inverse.