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] An amateur astronomer, he built a private observatory at his residence, Blenheim Palace.