George Spencer, 4th Duke of Marlborough

Styled by the courtesy title Marquess of Blandford from birth, he was the eldest son of Charles Spencer, 3rd Duke of Marlborough, and the Honourable Elizabeth Trevor, daughter of Thomas Trevor, 2nd Baron Trevor. His siblings were Charles, Diana and Elizabeth.

According to George III, who mentioned it to Fanny Burney,^[1] the Duke suffered from severe red-green colourblindness. As he was unable to tell scarlet from green, Fanny, therefore, remarked that this was unlucky for someone in possession of so sumptuous a home as Blenheim Palace.

Marlborough entered the Coldstream Guards in 1755 as an Ensign, becoming a Captain with the 20th Regiment of Foot the following year. After inheriting the dukedom in 1758, Marlborough took his seat in the House of Lords in 1760, becoming Lord-Lieutenant of Oxfordshire in that same year.^{[citation needed]} The following year, he bore the sceptre with the cross at the coronation of George III.^{[citation needed]} In 1762, he was made Lord Chamberlain as well as a Privy Counsellor, and after a year, resigned from this appointment to become Lord Privy Seal, a post he held until 1765.^{[citation needed]} An amateur astronomer, he built a private observatory at his residence, Blenheim Palace. He kept up a lively scientific correspondence with Hans Count von Brühl, another non-academic astronomer.^{[citation needed]}

The Duke was made a Knight of the Garter in 1768, and was elected to the Royal Society in 1786.^{[citation needed]}