Last week’s events in London raised a recurrent dilemma for journalists, including me. It is a huge story when a terrorist kills four people then is shot down in Palace Yard, Westminster. Yet dare we say how fortunate we are that since 9/11 Muslim terrorists have proved incapable of mounting an attack remotely as lethal as that on the Twin Towers? An intelligence officer told me recently that he worries far more about Russia than about Muslim suicidalists, and this must be the rational assessment. The public needs awakening to the menace posed by Vladimir Putin’s adventurism. Meanwhile, Khalid Masood’s dreadful deed reflects the flailings of a death cult. These will cause us regular surges of distress, but — to contradict David Cameron’s silly words — Muslim fanaticism does not constitute an ‘existential threat’. Last week nonetheless seemed the wrong time to suggest counting our blessings.

To the Donmar Warehouse for Roger Allam’s fabulous portrayal of Roy Jenkins in Steve Waters’s play Limehouse. It is an odd sensation, seeing an impersonation of someone I knew intimately. One of the most endearing aspects of Roy was his self-knowledge. He was well aware that he teetered on the brink of parody. Sheer brilliance and wit saved him from tipping over, however. He gave a masterclass in growing old, retaining curiosity about new people, places, books, films, plays. Another sure test of quality: he was unembarrassed by changing his mind. The rest of the SDP’s founders have receded. Shirley Williams will be remembered chiefly for her role in the 1960s devastation of state education. Nobody can remember why Bill Rodgers ever attracted a moment’s attention. David Owen never translated intelligence into effectiveness. Roy alone was a giant, despite failing to become prime minister. Kipling observed of a whist partner dead in Simla that he was ‘a fortnight fully to be missed’, which is as long as most absences are noticed. In Roy’s case, however, every day I yearn to hear what he thinks.

Lunch with Michael Heseltine, with whom I discover a new bond: as children we both had Trix trains, so much cooler than Hornby Dublo. We also liked making Keil Kraft balsa wood aircraft, a pastime to which Michael says he may return one day. Meanwhile, he is adoring his new role as an 84-year-old enfant terrible. When I suggest that he might settle for a quiet country life like mine, he stares with silent incredulity. Having many times holidayed, fished and shot with Tarzan, I can testify that he is wonderful company, touchingly honest about himself once one has broken through the perimeter barrier of shyness. But he never stops competing. I waste words suggesting that he should be as happy to cast a fly as catch a fish, or urge him to stop counting the cartridges it takes to kill a pheasant. He loves a fight, and is thrilled now to have one that keeps the Today radio car moored in his drive.

My favourite old warhorse tells me of a first encounter 20 years ago with the great Barbara Amiel, who is never less than a stimulating conversationalist. Her opening gambit as a dinner party neighbour was to ask this soldier, figuratively if not literally dripping with gold braid: ‘How old were you when you had your first sexual encounter?’ My friend responded without blinking: 14. In truth, he says now, he never got beyond a grope until four years after that, ‘but I felt I had to do my bit for Britain.’ By such inventive fluency are field marshals made.

Michael Howard (the good one, OM, CH, MC) is 94 and still razor-sharp, but depressed by echoes of the 1930s on both sides of the Atlantic — ‘and I am one of the few people still alive who watched it all happen’. At Wellington he learned, and recites to me from memory, lines from Auden’s 1937 ‘Danse Macabre’:

 It’s farewell to the drawing-room’s civilised cry,
The professor’s sensible whereto and why
For the Devil has broken parole and arisen,
He has dynamited his way out of prison.

Michael believes that President Trump will get his country into a war, and I hear that some of America’s top soldiers share this expectation.

In all wars soldiers have occasionally killed prisoners: what has changed is that helmet cameras have ended deniability. ‘Marine A’, Sergeant Alexander Blackman, should rightfully have been charged with manslaughter, not murder, for his killing of a wounded Taleban prisoner in Afghanistan, and thus his release from prison seems just. Yet the question nags me: if film existed of a Taleban shooting a wounded British prisoner in such circumstances, would the ‘Blackman defence’ have the smallest chance of getting him off?