I have been placed in draughty bedrooms next to women selling handbags and sunny kitchens beside men modelling pyjamas. I’ve made friends with young couples selling recycled cardboard furniture and marvelled that the most popular item in the place appears to be handmade dog biscuits. I’ve learned a lot about shopping psychology in the strand of ‘flash retail’-otherwise known as the private-house Christmas fair-not least that, although I’m a happy wholesaler, I’m a rubbish retailer.

I thought I would love having a stall, feeding as it does into the childhood fantasy of owning a shop, but it turns out that my enjoyment depends on which side of the trestle table I’m standing. I may enjoy setting up the stall (selling books published by some great friends along with some games I produce) and I like wrapping items and putting them into crisp carrier bags. I love talking to customers. But I don’t enjoy asking people for money.

I know that this is absurd. As absurd as feeling that, if you flatter your products, it feels as if you’re showing off about your children. On the whole, any squeamishness can be offset by the thrill of using the cordless credit-card machine, but there remains the moment when an undecided customer and you dance around. Is she doing the shopping equivalent of ‘I’m just going to get a drink’ or is she about to commit? I never know and tend to turn my back.

The credit-card machine rarely works at the private country house, this usually being in such an idyllic setting that there’s no mobile signal. Frantic stallholders can be found outside, in the driving rain, waving the machine above their heads.

They’re having to do this on account of the shopper who declares that everything on sale is perfect for her long list of relatives, but who also prefaces all transactions with the ominous words: ‘I’m so silly-I’ve come without any cash.’ I might say ‘oh, just have it then’ in order to conclude what has become, to me, an embarras-sing conversation, except that I know from experience that nothing makes an item more unwanted than if it’s free. I learnt this early on in my retail experiments when I had an stall on the Portobello Road. My brother-in-law Barnaby sold beautiful North African textiles and I sold chipped china-but not very much of it. We enjoyed studying shopping behaviour, with Italians often being the most unfathomable.

One Florentine bargained Barnaby down from £12 to £2 for a much-rivetted saucer-a conversation that took at least 15 minutes and which they both enjoyed enormously. At the £2 mark, she peered at it for the umpteenth time before finally putting it back with a dismissive but emphatic shrug. Seeing her later as we were packing up, he rushed down the street in order to give it to her for nothing. But this obviously made it so undesirable that she refused it.

Bargaining is second nature to Barnaby, but I loathe it, both as a seller and a buyer. Not perhaps as much as my brother, who became so exasperated by the traders in Morocco that he cut his holiday short. He can’t understand a country where the principle of a genuine price is entirely replaced by the game of who breaks first. Or this is how he sees it. On the last day of his abbreviated holiday, he was very proud of finally managing to buy some bowls for a tenth of the original price, only to find them cheaper in the airport shop.

He would prefer the private Christmas sale where the prices are firmly displayed-even though, despite this, almost everybody asks how much things cost, which always makes me wonder if they’re trying to bargain, in an English way. True, you might get a few pounds off when the weary stallholder is packing up, which is also the most dangerous time for the stallholder whose heart is on the wrong side of the table. Last week, I came home with some dog biscuits and a very peculiar cardboard chair.

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