There's nothing like five weeks in court - as I spent with the Hamiltons - for making you feel utterly puny. Up in the witness box or down with the groundlings, the litany seems the same. "I can't remember." "I have no memory of that." "I have no such recollection." "I definitely have no such recollection." What happened five or 10 or 15 years ago? The fogs of forgetfulness fall constantly over witnesses on every side. Dunno. Search me, guv. There's a dreadful truth about human inadequacy lurking here. We're supposed to be men and women of intelligence, summoned to testify with extreme precision. The judge says he lays great store by consistency in detail. But how is such a miraculous state of grace to be produced?  Mr Desmond Browne QC (for the plaintiff) keeps calling Miss Bozak, Miss Bond and vice versa. Two key witnesses; one tongue lock. My wife in the gallery persists in her belief that he's really Dennis Browne. (Some confusion with Dirty Den?) My lord on the bench introduces me solemnly as "editor of the Guardian for 20 days," which would be swift going, even on the old Daily Express.  Memory as the millennium ends seems a suitable subject: intractable in its furthest scientific reaches. The definitive learned journal, Learning and Memory, constantly promises enlightenment. Try the essay on "the effect of varying the intensity and train frequency of forelimb and cerebelar crossing fiber conditioning stimuli on the latency of conditioned eye-block responses in decerebrate ferrets". You may be suitably instructed about "interneurons and food averse conditioning in the slug brain" but you will find very little that relates to Court 13.  Only, perhaps, Hamann, Cahill, McGough and Squire on "intact enhancement of declarative memory for emotional material in amnesia," which means that, when the team told their forgetful subjects "emotionally arousing stories" with video slides attached, the images lingered longer. That is not a shattering conclusion. We assume that it's the high drama of our lives (professional and personal) which defines the scenes we do remember. The death of Kennedy, the moment 10 Christmases ago when Romania was suddenly free: or, closer to home, the births and crises of sickness.  And yet, for me, the most vivid memories are often oddly tangential. I don't remember what my mother said 50 years ago when she told us our father had died. I do remember sitting in the bay window overlooking the lawn a few hours later and seeing his Biro pen and asking whether it could be mine now. "Yes, of course." And then feeling selfish and petty and suddenly overcome with grief.  I remember my father in only one moment, when he'd bought another second-hand car (as he did every six months) and was showing me the gears. It was an Opel with a gear shift on the steering wheel. Slam the car door and he is gone. Why is memory so full of shifting sands? I have a good one, but stocked with useless facts. The assorted filmo-graphy of Rhonda Fleming; the real names of Tony Curtis and Walter Matthau. (Bernie Schwarz: Wally Matuschanskayasky).  But it is a particular kind of memory. Faces? I could never have been a politician (or, if so, only David Steel, who once told me he was hopeless at putting names to faces). Those with that gift are kings. I once, after an absence of years, wandered into the Ledra Palace hotel in Nicosia, and there at reception was Pan, the chief concierge. "Ah, Mr Preston. Nice to see you again." One face among thousands passing through. He should have been president.  Nor is there the consistency of a whole vision on call. Does such a thing exist? Dennis Potter's Blue Remembered Hills, an evocation of a rural life so complete in its detail, so passionate in its re-creation, that you wondered where memory ended and fiction began. Does any child have the capacity to deliver back intact a world that is decades gone?  I remember the first piece from Bosnia that Maggie O'Kane filed for the Guardian, but when I look through the yellowed cuttings of editorials, I can read a piece and not know that I wrote it. I can remember shaking Richard Nixon's cold, limp hand, but not a sentence that he said. I can remember ripping the agency tape of Harold Wilson's resignation from the wire service, but nothing of the paper that followed.  And family memories are a compilation of all these things, as shared patchwork. My wife remembers with uncanny accuracy what we ate or wore 20 years ago. She remembers where I was when our first son was born (at the office, working) and where when the second son followed (downstairs, boiling water). Things I choose to forget; just, alas, as I choose to let slip the time when she walked down the hill to the hospital, carrying a suitcase, to have our twins induced (I was in the office, working).  Are such omissions an acknowledgement of frailty? Naturally so. The taunting thing about memory is the essential frailty that dogs its every lurch into the past. Sometimes you can recall pivotal scenes which other players have totally forgotten. (I summoned back one in the Hamilton saga). But sometimes the screen mists and fades without explanation. What do I remember of my longest day in war, twice strafed by Indian jets in a Pakistani ditch? I remember cracking my teeth on a metal screw in the ravioli at Flashman's, Rawalpindi.  Goodbye to the old century. We remember it after a fashion. But the most terrifying blight is not to remember it at all. I once had lunch with one of my heroes, Kenneth Millar, the writer Ross MacDonald, whose best-selling pitch was the haunting return of buried evils. Within a couple of years, Alzheimer's destroyed him. It was, and is, the purest tragedy, the annihilation of being. A witness no more: not even a slug or a ferret. A mind full of punctilious richness shut down like a broken computer. Memory full, memory wiped.