Christian Peper in his edition of Toynbee’s correspondence with Columba Cary-Elwes, which lasted from 1937 until Toynbee’s incapacitation in 1974:
There is a curious parallel to this unbroken [not quite unbroken] series of letters in the correspondence of another man of letters with another Yorkshire clergyman: Horace Walpole and the Reverend William Mason exchanged frequent letters from 1763 until the year before their deaths in 1797. Needless to say, the eighteenth-century letters were concerned with more mundane matters than theology.
He could have added that Mrs Paget Toynbee (Helen Toynbee, 1868-1910), the wife of Arnold Toynbee’s paternal uncle, the Dante scholar Paget Toynbee (1855-1932), edited Walpole’s correspondence. Paget Toynbee took over her work when she died.
Christian B Peper, editor, An Historian’s Conscience, The Correspondence of Arnold J Toynbee and Columba Cary-Elwes, Monk of Ampleforth, with a Foreword by Lawrence L Toynbee, OUP, by arrangement with Beacon Press, Boston, 1986, posthumous