Question: The "black spider" memos are letters and memos, to British government ministers and politicians over the years, written by Charles, Prince of Wales, the eldest child and heir apparent of who?

Context paragraphs:
Black spider memos: The "black spider" memos are letters and memos written by Charles, Prince of Wales, to British government ministers and politicians over the years.  As the modern British monarch remains politically neutral by tradition, the letters are controversial because of Prince of Wales' position as the eldest child of the British monarch Queen Elizabeth II and heir apparent to the British throne.

Diana, Princess of Wales: Diana, Princess of Wales (Diana Frances; "née" Spencer; 1 July 1961 – 31 August 1997), was a member of the British royal family as the first wife of Charles, Prince of Wales, who is the eldest child and heir apparent of Queen Elizabeth II.

Norwegian royal family: The Norwegian Royal Family is the family of the Norwegian monarch.  In Norway there is a distinction between the Royal House and the Royal Family.  The Royal House includes only the monarch and their spouse, the heir apparent and their spouse, and the heir apparent's eldest child.  The remaining Royal Family includes also all other children, grandchildren and siblings of the monarch, along with their spouses and widows or widowers.

Duke of Rothesay: Duke of Rothesay (Scottish Gaelic: "Diùc Baile Bhòid" , Scots: "Duik o Rothesay" ) is a dynastic title of the heir apparent to the British throne, currently Prince Charles.  It was a title of the heir apparent to the throne of the Kingdom of Scotland before 1707, of the Kingdom of Great Britain from 1707 to 1801, and now of the United Kingdom of Great Britain and Northern Ireland.  It is the title mandated for use by the heir apparent when in Scotland, in preference to the titles "Duke of Cornwall" (which also belongs to the eldest living son of the monarch, when and only when he is also heir apparent, by right) and "Prince of Wales" (traditionally granted to the heir apparent), which are used in the rest of the United Kingdom and overseas.  The Duke of Rothesay also holds other Scottish titles, including those of Earl of Carrick, Baron of Renfrew, Lord of the Isles and Prince and Great Steward of Scotland.  The title is named after Rothesay on the Isle of Bute, Argyll and Bute, but is not associated with any legal entity or landed property, unlike the Duchy of Cornwall.

James of Aragon (monk): James of Aragon (29 September 1296 – July 1334) was the eldest child of King James II.  His mother was Blanche of Naples, the second of his father's four wives.  As the king's eldest son, James was not only an "infante" but also heir apparent to the Crown of Aragon, a realm stretching from north-eastern Spain to Sardinia and Corsica.  He is best known for his unexpected decision to renounce his marriage and right to the throne and become a monk.

Afonso, Prince Imperial of Brazil: Dom Afonso (23 February 1845 – 11 June 1847) was the Prince Imperial and heir apparent to the throne of the Empire of Brazil.  Born in Rio de Janeiro, he was the eldest child of Emperor Dom Pedro II and Dona Teresa Cristina of the Two Sicilies, and thus a member of the Brazilian branch of the House of Braganza.

Crown Prince of Thailand: The Crown Prince of Thailand (or Siam; Thai: สยามมกุฎราชกุมาร ; rtgs: Sayammakutratchakuman ) is a title held by the heir apparent to the Thai throne.  First created by King Chulalongkorn (Rama V) in 1886, for his son Prince Maha Vajirunhis, the king's eldest son by a royal wife Queen Savang Vadhana.  Prior to this, the Siamese throne did not have a law or formal system regulating the royal succession.  In 1688 King Petracha of Ayutthaya created the title of Front Palace, which by the Rattanakosin period had become the main title granted to the heir presumptive to the throne.  However few Front Palaces have succeeded to the throne this way, with the exception of King Buddha Loetla Nabhalai (Rama II) in 1809.  After the Front Palace crisis in 1875, the title of Front Palace was abolished and replaced with the title of Crown Prince, who became heir apparent to the throne.

Charles, Prince of Wales: Charles, Prince of Wales (Charles Philip Arthur George; born 14 November 1948) is the eldest child and heir apparent of Queen Elizabeth II.  Known alternatively in Cornwall as Duke of Cornwall and in Scotland as Duke of Rothesay, he is the longest-serving heir apparent in British history, having held the position since 1952.  He is also the oldest person to be next in line to the throne since Sophia of Hanover (the heir presumptive to Queen Anne), who died in 1714 at the age of 83.

Prince of Beira: Prince of Beira (Portuguese: "Príncipe da Beira" ) is a title traditionally granted to the heir apparent of the heir apparent to the throne of Portugal.  The title's original use that it be granted on the eldest daughter of the reigning monarch of Portugal.  Tied with the title of Prince of Beira, is Duke of Barcelos, as heir to the Duke of Braganza and Prince of Brazil ("later" Prince Royal of Portugal).  The current Prince of Beira is Prince Afonso, the eldest son of Duarte Pio, Duke of Braganza.

Camilla, Duchess of Cornwall: Camilla, Duchess of Cornwall, ("née" Camilla Rosemary Shand, previously Parker Bowles; born 17 July 1947), is the second wife of Charles, Prince of Wales, the eldest child and heir apparent of Queen Elizabeth II.  Instead of using the title of Princess of Wales, she uses the title Duchess of Cornwall, her husband's secondary designation.  In Scotland, she is known as the Duchess of Rothesay.  In the event of Charles acceding to the throne, Camilla would become a queen consort; however, an official statement issued by Clarence House on the day of her marriage to Charles announced that she would be known as the Princess Consort.

Supporting paragraphs: Black spider memos Charles, Prince of Wales
Answer: Queen Elizabeth II