https://chesshistory.com/winter/extra/morgan.html
I came across this (I feel I should have been more familiar with him) when looking up details of chess columns in the literary magazine Time and Tide:
https://en.wikipedia.org/wiki/Time_and_Tide_(magazine)
Prompted by Leonard's delightful recollections of the trials and tribulations of being a chess columnist in the era of typewriters, I had visions of D.J. Morgan likewise wrestling with similar problems.
I found one D.J. Morgan column in Time and Tide from 1957, and was wondering if anyone knows the dates he was a columnist there?
On that page, Winter passes on a memoir from Morgan's son ("the eminent historian Kenneth O. Morgan"):
He had strong political interests (left-wing Labour) and, as chess editor of Lady Rhondda’s Time and Tide for a while, was delighted when readers of that right-wing journal objected to so many Russians appearing in his column. He responded by doubling the number.
There is an interesting tip-off there that the historian William D. Rubinstein is clearly a chess player as an anecdote is related that the son of D.J. Morgan appointed Rubinstein as a history professor at Aberystwyth in 1995, and Rubinstein said that he read D.J.'s columns "avidly". The son relates: "For him, I was just the son of the famous D.J. Morgan and I was overjoyed to know it."
Looking further into the chess background of William D. Rubinstein, is he the same researcher who in 1970 was carrying out surveys on the "greatest" chess players by writing to the greatest living at the time?
https://en.wikipedia.org/wiki/William_Rubinstein
https://www.chesshistory.com/winter/extra/greatest.html
I suspect they are the same, but the name is quite common so it is hard to be sure.