This week, a cache of letters was put up for sale at Christie's, where it fetched £3.8m. The letters didn't comprise a correspondence or a sequence, more a lucky dip of one-off communications from famous people in history. There was a note from John Donne to Lady Kingsmill in 1624, offering his condolences on the death of her husband; but perhaps the star of the show was a love letter from Napoleon, apologising to a sulky Josephine for the impression that he was only interested in her cash.
This glorious magpie muddle of a collection was put together by the late Albin Schram, a man whose desire to possess intimate fragments of someone else's past was apparently whetted in 1973 by the Napoleon letter. He spent the next 32 years, until his death, roaming the auction rooms of Europe, snapping up the waifs and strays of other people's paper trails.
That these bits of parchment were important to Mr Schram not as a financial investment but as something more intimate is suggested by the fact that, rather than storing them in the bank, he liked to keep them close, in a filing cabinet at his Lausanne home. Although there's no way of knowing, I like to think of him breaking off his morning constitutional around the lake in order to hurry home to spend more time reading, stroking - even sniffing - these last relics of the great.
For there is something about a letter - as opposed to its facsimile or transcription - which gives you a tangible link with the past. Where your finger now lightly brushes against the page is exactly where Donne's or Napoleon's own digit once rested. It's the next best thing to owning St Francis's toenails. And then there's the rich mulch of clues to the writer's personality. Carefully "crossed" letters - designed to save on postage - suggest an economical mind which, even at the height of passion, refuses quite to break down or let go. A stamp stuck on skew-whiff, by contrast, implies a correspondent fumble-fingered with desire or rage. A sprawling, curlicued signature taking up half the page hints at an ego looking for worlds to conquer. Or perhaps the opposite - a shivering soul taking refuge in grand gestures. Either way, you don't get such gold dust from an email.
I experienced this excitement for myself six years ago, when I remortgaged my flat and bought all the known letters ever written by Mrs Beeton and her husband, for a biography I was then researching. A transcription might have told me that Isabella crossed her letters to save on postage while her husband could never be bothered to date his. But it was only once I held the documents in my hand that I saw that she used blue ink while he opted for sketchy pencil. That told me more than any amount of careful textual scholarship ever could.
Of course, it's easy to fetishise letters, to imagine that they grant us access to the extraordinary spirit of the person who wrote them. But the great, just like the rest of us, have a disappointing knack of being dull in their private correspondence, writing about the weather, next year's holiday and what they fancy for supper. In 2001 a number of unpublished letters by George Eliot were acquired by the British Library. As one of the first people to see them I was excited and alarmed in equal measure. Selfishly, having recently published a biography of Eliot, the last thing I wanted was to discover new information which challenged the picture of the novelist that I had only just put before the world.
In the event I need not have worried. Not because the new letters said nothing, but because what they revealed amplified rather than qualified what I already knew about Eliot during the quiet, domestically-oriented years when she wrote them. And that, if you think about it, is what letters mostly do. While the biographer in me longs for a piece of correspondence which reveals something previously unknown - an illegitimate baby, alcoholism, evidence of a dark, malicious spirit - the realist and letter writer in me accepts that human nature is too insistent to allow that to happen.
Personality, as Eliot herself was keen to show, is spun out of a fine web of associations and habits which make it unlikely that information contained in a single document will unravel the whole effect. No matter how carefully we guard the world from our secrets, the chances are that the world already knows them. Not because it has seen some thrillingly revealing letters, but because everything contained within them is already available to any spectator who cares to watch us go about our business.
And that's why Mr Schram's obsession with hunting down single letters strikes me as strange, more akin to stamp collecting than sustained historical or psychological enquiry. Taken out of context, orphaned from its fellows, the single letter, far from offering a snapshot of the writer's state at a particular moment, is likely to conceal more than it reveals. The people and situations referred to become no more than baffling crossword clues; and the letter, far from taking its place as a team player in the great game of understanding the past, becomes simply an autograph with a bit of desultory chat attached.
· Kathryn Hughes is the author of The Short Life and Long Times of Mrs Beeton
