His brother Dick (b.1910) wrote in 1984:
"I knew that John had got into some trouble during the war...a letter going the wrong way. As I remember the story, he had written a flippant letter from that prep-school in Wales to a Bradfield/Balliol friend in the navy with the wrong address. The letter was returned to "John" at XYZ village in Wales. The post mistress knew only one John, the squire, who read the letter, found a mocking thumbnail sketch of himself and also of the head master of the prep school AND waggery and scorn of the Government and the war. The letter was sent on to the Head Master who passed it to the police and it eventually surfaced on the desk of Captain Jim Hale, Grenadier Guards and MI5. Jim had collected a vehicle and a FANY and motored to Wales to make sure it was just one of the Usbornes he knew, and therefore harmless, as it was, and that's the end, except John had been sacked from the school.
Thinking the intended recipient of the letter had been John Mcnair (later Lord McNair) and meeting John McN. at Henry's camp recently, I asked him for chapter and verse. He said no, it wasn't me it was Morrice James
(later Lord Saint Brides), and he gave me an address. John said that he had talked about the letter fairly recently with Morrice who told him that some years after the war, when his feet were on the Foreign office ladder, his boss had said to him: "By the way, young man, you'll be glad to know that we have officially destroyed the file about that letter written to you by John Usborne".
I have Paula's permission to pass this on for the family archives. I hadn't realised that John had been a conscientious objector. I knew he had that heart problem. Paula tells me that, after his retreat from the Wales job, he had applied to join the Army Medical as a stretcher bearer but had been ploughed on his medical....heart. Thence to more school-mastering. He had received some white feathers at Windlesham, but none from friends".
Morrice James wrote to Dick from California on October 1st 1984:
Broadly your version is right. But (a) John was replying to a letter which I had written him, in September 1940 when I was an Ordinary Signalman ("You,re a college boy; do you think you could manage Morse?") under basic training at the RN barracks at Devonport. In my letter I had severely criticised the Navy for its organisational short-comings, for wasting its recruit's precious time. There were not enough instructors, so sometimes it was: "All right, you lot, keep out of sight until smoke. Oh and for Gawd's sake don't let no officer see you". (b) John's reply never reached me since, by the time it arrived at Devonport, I'd disappeared from the barrack books on transfer to the Royal Marines. (c) In his reply John must have echoed, or quoted my strictures on the Navy since the only serious charge that could possibly be leveled against him was that he had written to a naval rating in wartime in a manner likely to cause alarm and despondency. (d) Yes, he was a conscientious objector at that time. I suppose it was for that reason that his Head Master (and the Head Master's wife) and the local squire were all against him, and must have relished the thought that, in making trouble for him, they were doing no more than their patriotic duty. I remember John telling me that, at their farewell interview, the Head Master was all smiles, until he delivered (almost as an afterthought) his carefully prepared punch line: "Oh, by the way, I've given the police that seditious letter you wrote to a naval rating in Devonport".