In all the travelling I’ve done for this job, I’ve never quite found the perfect piece of weekend luggage. I’ve fantasised about it, as you do. Or I do. Frankly I’m amazed how many women’s fantasies seem to involve handcuffs, murder or finding themselves at the head of the Christian Louboutin sample sale queue; mine are about cubic centimetres, hardware and the flint-faced woman at the Alitalia check-in eyeing up my luggage and finally saying: “Yes, madam, you may take that on board, in which case I will not hurl it on to this conveyor belt and watch it tumble into an abyss of confusion and thence into lost-property limbo.”

It is, I admit, a dull fantasy, but I share it with you today because nine months ago I happened to mention my eternal quest for the Perfect Piece of Weekend Luggage to the Louis Vuitton PR in London. Normally this is the type of high-risk gambit guaranteed either to wind up a meeting pretty damn pronto or, if you’re unlucky and the PR is in to Mission: Impossible, prolong it by several hours while he/she parades every model ever designed by the company to try to prove you wrong.

But this time my strategy threw up something much more intriguing. Instead of dragging me back to the showroom to look at another 197 bags, those canny PRs asked me to come up with a wishlist for the Perfect Piece of Weekend Luggage, with a view to auctioning the finished item – a one-off for charity.

Next thing I knew I was in Asnières, outside Paris, at the Louis Vuitton workshops, having highly technical discussions with the Vuitton team (by now we had been joined by two French PRs and Jean-Philippe Martin, the designer assigned to this project). I say the next thing, but in reality it was several weeks after that first discussion, long enough for me to pester my friends, family and everyone who knew me about what they’d like from a weekend bag. And when it became clear that including all of everyone’s deepest desires would make it weigh about 11 tonnes, I began again.

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• Pictures: The special Louis Vuitton suitcase

Actually the conversations weren’t that technical. At least my contribution wasn’t, consisting as it did of yes, no, not sure, and purple, loving it! It was yes to wheels, because while they take up valuable space, the amount of hanging around and walking to gate 97 that is part of the glamour of today’s travel makes them mandatory. Yes to a skinny patent clutch in monogrammed vernis with a detachable gold chain (because, er, I love it). Yes to a cashmere wrap/blanket and eye mask for the plane (for that luxurious cocoon feeling even when you’re slumming at the back). Yes to a slim-line laptop case and a separate holder for all the cables, yes to a transparent cosmetics bag with matching trim, no to hangers and suit bags, on the ground that no one uses the hangers that come with suitcases and that if we chucked in all our hearts’ desires, there wouldn’t be any space for clothes. We discussed compartments at length and, in the end, restricted the number to three – one for business, one for personal use and one for travel documents – to provide maximum flexibility, and made sure that everything fitted into a bag that would go into the overhead lockers. There was a question-mark over the classic monogram print vthe Damier check (designed by Louis’ son George in 1888) until we agreed that if this were to be a Vuitton showpiece, it had to be the monogram (designed by Louis’ grandson Gaston in 1896).

I agonised over the trim, because after initially falling for the purple leather samples, I had a wobble when Jean-Philippe appeared with a book of orange swatches that looked gorgeous. Then there was a crisis with the lining (all special orders are made with luxurious Alcantara); should it be dark purple, lilac or putty? Or orange? I’m telling you, this bespoke business is exhausting. One decision, however, was easy. Team Vuitton wanted ostrich for the trim, because it screams luxury. I didn’t because – well, I don’t like ostrich. And what is the point of bespoke if you can’t behave like an autocrat?

Then I toured the Asnières workshops, where 220 men and women produce by hand Vuitton’s prototypes and the 550 or so special orders that are placed annually (the rest of LV’s output is scattered among 15 factories in France, Spain and Italy). It is at Asnières’s special order department that Sofia Coppola’s customised case for her Bose speakers was made, and Karl Lagerfeld had special iPod holders that carry 20 at a time designed. It’s where one client came for a travelling solution for the 100 watches he takes everywhere, and another when he needed – and who doesn’t? – a Vuitton case for a birthday cake. It was to Louis Vuitton that Napoleon III’s wife, Princess Eugénie, turned for someone to oversee her cases in the 1850s (Vuitton began his career as a professional packer, a canny move at a time when the upper echelons travelled with 50 or 60 pieces of luggage), to Vuitton that everyone from Cary Grant to Marilyn Monroe went once they’d arrived, and shortly before they were due to set off somewhere else. And it is to Vuitton that a new generation of super-rich are flocking now that trunks (and private air travel) are newly fashionable.

I saw the hammer and nails they still use on those trunks, the eight processes that go into making just the corner covers; the two kinds of wood – poplar and okoume, both chosen for lightness – used for hard luggage and watched as two men hammered and glued the signature featherweight, waterproof coated canvas that Vuitton invented more than a century ago on to a wooden frame, then fixed in place the binding that attaches the lid to the case, a technique Vuitton developed to circumvent the need for hinges, which would eventually rust.

According to legend, Vuitton’s was the only luggage to survive the sinking of the Titanic. If true, congratulations to the marketing team for not using this nugget in their ads. The point is that the respect these artisans have for their craft transcends trends, and means that whether one thinks of Audrey Hepburn, or a WAG, travelling with the stuff, ultimately the product defies tribal stereotyping.

As months went by, emails flew back and forth, the bag took shape and at some point CNN got interested in the story and filmed some of our meetings. No pressure, then. It was with considerable trepidation that I went to see the prototype when I was in Paris for the shows in October. I needn’t have fretted. Nine months almost to the day, this baby is, in my humble view, the way to go – and purple was definitely the right choice. I won’t get to use this Perfect Piece (that’s altruism for you), but someone generous will. Someone generous and with excellent taste. I hope they enjoy it.

— For more pictures visit www.louisvuitton.com

The auction: how to bid for the Ultimate Travel Bag

The Ultimate Travel Bag will be auctioned online and by phone. It will be on display until December 18 at Louis Vuitton, 190-192 Sloane Street, London SW1. All the proceeds will go directly to CLIC Sargent, the charity that helps children with cancer and leukaemia, and their families. To bid, go to www.clicsargent.org.uk between now and midnight (UK time), December 18. To bid by phone call 020-8752 2883. The starting reserve is set at £10,000. The website and telephone voicemail will include a daily update on the new daily reserve based on previous bids accepted.

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