John Davies Knatchbull Lloyd (28 April 1900 – 13 December 1978), generally known as J. D. K. Lloyd, was born on 28 April 1900 at Plas Trefaldwyn, Montgomery in the present day county of Powys in mid Wales. He was the elder son (his younger brother was Wyndham Edward Buckley Lloyd, F.R.C.S., L.R.C.P. 1901-1980) of John Maurice Edward Lloyd, M.A., of Plas Trefaldwyn, Montgomeryshire, a barrister of Lincoln's Inn. He went to Winchester School and Trinity College Oxford (M.A.), and was a member of the Hypocrites' Club alongside Evelyn Waugh, Anthony Powell, Robert Byron and many other prominent figures of the time; he received the nickname 'the Widow' in reference to a shaving lotion, 'The Widow Lloyd's Euxesis'. Lloyd's name appears in conjunction with this nickname in the journals and letters of many of his contemporaries for decades afterward. Following his education he embarked on a long life devoted to antiquarian research and to his community.
J. D. K. Lloyd wrote many articles and guides to Montgomery. He donated Dolforwyn Castle to the Welsh Ancient Monument Board (now Cadw) in 1955.
He died on 13 December 1978.