Lenox Simpson was the son of Clare Lenox-Simpson, who had been in the Chinese Maritime Customs Service since 1861; he had a brother, Evelyn, a mining engineer who worked in China, and a sister, Esme.

[2] Lenox Simpson left the Chinese Maritime Customs Service in 1901, perhaps connected with zealous looting [citation needed] after the siege of the Legations in 1900.

One historian calls him "the consummate treaty port jobbing hack, writing commentaries, begging for newspaper work, penning novels... and serving as Daily Telegraph correspondent in Beijing from 1911 to 1914.

[6] His work Indiscreet Letters from Peking is widely cited as an eyewitness account of the events during the siege of the Legations in 1900, but two scholars have cast doubt on its reliability.

The Oxford English Dictionary cities his Why China Sees Red as an early example of use of the word term warlord, though The New York Times had used it earlier.