Surname of the royal family?

The House of Windsor, formerly Saxe-Coburg and Gotha, succeeded the House of Hanover on the death of its last monarch, Queen Victoria. The original dynastic name of Victoria's German-born husband, Albert, Saxe-Coburg and Gotha was changed to Windsor during the anti-German atmosphere of World War I by their grandson King George V.

On 17 July 1917, King George V issued a Proclamation which stated that the male line descendants of the royal family would bear the surname Windsor:

from the date of this Our Royal Proclamation Our House and Family shall be styled and known as the House and Family of Windsor, and that all the descendants in the male line of Our said Grandmother Queen Victoria who are subjects of these Realms, other than female descendants who may marry or may have married, shall bear the said Name of Windsor
A few months later, King George V issued Letters Patent on 30 October 1917 which limited the title 'Prince' and the style 'Royal Highness' to the children of a sovereign, the children of sons of a sovereign and the eldest living son of the eldest son of the Prince of Wales. HH Prince Alastair of Connaught (1914-1943), grandson of HRH Prince Arthur, Duke of Connaught (Queen Victoria's fourth son), became the first member of the royal family to use the surname Windsor in lieu of his princely title. It has been suggested that it was a misinterpretation of these latest Letters Patent which led to HH Prince Alastair (for such he was based on practise going back to the time of King George I's accession in 1714 and which practise was confirmed in Queen Victoria's Letters Patent of 30 January 1864; source: "The Princes of Great Britain" article in Burke's Peerage 1963 edition, pp xxvii-xxxii) being denied his princely title. However, as he was the son and heir of a peeress (Princess Alexandra, Duchess of Fife), he was allowed the courtesy use of his mother's subsidiary title and became Alastair Windsor, styled Earl of Macduff.

On 11 December 1917, it was further decided by Letters Patent that:

the grandchildren of the sons of any such Sovereign in the direct male line (save only the eldest living son of the eldest son of the Prince of Wales) shall have the style and title enjoyed by the children of Dukes.
In 1952, Queen Elizabeth II confirmed her grandfather's decision that the royal family's surname would continue to be Windsor. Her Majesty declared on 9 April 1952 that it was:

her Will and Pleasure that She and Her Children shall be styled and known as the House and Family of Windsor, and that Her descendants other than female descendants who marry and their descendants shall bear the name of Windsor.
A few years later, HM The Queen modified this statement by issuing Letters Patent in February 1960 which stated in part:

while I and my children will continue to be styled and known as the House and Family of Windsor, my descendants, other than descendants enjoying the style, title or attributes of Royal Highness and the titular dignity of Prince or Princess, and female descendants who marry and their descendants, shall bear the name Mountbatten-Windsor.
Did this mean that the name of some members of the royal family changed from "Windsor" to "Mountbatten-Windsor"? Some people contend that the goal of this declaration was meant to not only change the surname of the children of HM The Queen but those of her male-line descendants as well. At Princess Anne's wedding in November 1974, Anne signed the marriage register 'Anne', without a surname. It was the registrar who filled in her names as 'Anne Elizabeth Alice Louise Mountbatten-Windsor'. According to a Buckingham Palace statement issued in October 1975, the specific addition of the surname 'Mountbatten-Windsor' was "the Queen's decision that this should be done". Further, HM The Queen consulted with the acting Prime Minister to confirm whether all her children would have the surname Mountbatten-Windsor. She received the following reply:

"The effect of Your Majesty's Declaration is that all the children of Your Majesty who may at any time need a surname have the surnames of Mountbatten-Windsor."
(Prince Philip: A Biography, by Denis Judd, London: Michael John, 1980, page 196)
It would seem that the surname of HM The Queen's children is whatever HM wishes. Legally and constitutionally, however, the Queen cannot do as she wishes. The surname of the Queen's children is Mountbatten-Windsor in practise and has appeared three times: at Princess Anne's first marriage in 1974, on Prince Andrew's marriage register in 1986, and when the banns were read prior to Princess Anne's second marriage to Commander Laurence in 1992. (When the Prince of Wales married in 1982, he signed the register as "Charles P" and the registrar filled in his name as "His Royal Highness Prince Charles Philip Arthur George The Prince of Wales".) Nonetheless, the family name remains legally Windsor because there hasn't been any modification or clarification to the Letters Patent of 1960.

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