The nine volumes of Agate's diaries and letters cover the British theatre of his time and non-theatrical interests such as sports, social gossip and private preoccupations with health and finances.

Gustave Garcia, nephew to the prima donna Maria Malibran, was Charles's lifelong friend after they were apprenticed together in the cotton warehouse.

[1] In his spare time he was a regular theatre goer, and admired and longed to emulate the critical writing of George Bernard Shaw in The Saturday Review.

[1] Even as a junior critic Agate did not hesitate to give bad notices to the leading figures of the English stage when he thought it justified.

"[4] Later, Agate was bested by Lilian Braithwaite, who responded to his assertion that she was "the second most beautiful woman in London" by replying, "I shall long cherish that, coming from our second-best theatre critic.

"[5] In his early twenties, Agate wrote a play, The After Years, which his biographer, Ivor Brown describes as "less than successfully realized".

"[7] Agate's fluency in French and knowledge of horses found him a successful job as a hay procurer, described in the first volume of his Ego.

His system of accounting for wartime hay purchases in a foreign land was eventually recognised by the War Office and made into an official handbook.

In the same year, while still serving in France, Agate married Sidonie Joséphine Edmée Mourret-Castillon, daughter of a rich landowner.

[9] In 1921 he secured the post with The Saturday Review once held by Shaw (and then by Max Beerbohm), and in 1923 he moved to The Sunday Times, where he remained theatre critic for the rest of his life.

The resulting narrative, with fragments of hilarious mock-fiction, ranks with Pepys's diary for vividness of characterization and fullness of historical detail".

Anecdotes of the day's news, excerpts from his voluminous correspondence with readers of his reviews and books, frank and often amusing ruminations on his health (he was a hypochondriac and obsessive-compulsive) and poor financial state abound.

Many of his diary entries mention his friends Herbert van Thal, George Lyttelton, Dent and Pavia, and Edward Agate, his much-loved brother.

He died in June 1947 suddenly at his home in Holborn, London, at the age of 69, shortly after completing his ninth Ego volume.