Sir Alan Frederick "Tommy" Lascelles, was a British courtier and civil servant who held several positions in the first half of the twentieth century, culminating in his position as Private Secretary to both George VI and Elizabeth II. In 1950, he wrote the Lascelles Principles in a letter to the editor of The Times, using the pen-name "Senex".

The private secretary to the sovereign is the senior operational member of the Royal Household of the sovereign of the United Kingdom. The private secretary is the principal channel of communication between the monarch and the governments in most of the Commonwealth realms. They also have responsibility for the official programme and correspondence of the sovereign. Through these roles the position wields considerable influence. This is one of the most senior positions within the Royal Household.