It's mid-August, and temperatures are hovering around 25 degrees Celsius. The sun is shining brightly, the harvest is ripening in the fields and everyone is heading off on their summer holidays. What better time is there to start selling Christmas-tree decorations and yuletide ephemera? I kid you not. Harrods and Selfridges department stores have both decided that mid-August is a ripe time to launch their festive shops. Santa rode into Harrods last Tuesday, not on a reindeer, but on a zebra, to open a department selling tinsel, angels, cuddly polar bears and novelty Father Christmases. To generate a festive mood, the store piped out 'seasonal' songs such as Santa Baby. Not to be outdone, Selfridges opened its shop on Wednesday, reportedly selling thousands of baubles. The usual decorations are on offer, but it seems extravagance is the key this year, with gaudy baubles, tinsel and foil aplenty. The upmarket department stores usually don't foist Christmas on their shoppers until late September, when Brits start to feel Christmassey - namely, when it starts to get wet and cold. So why now, before even Guy Fawkes night and Halloween? Believe it or not, there is method in their madness. It's all down to tourism. Apparently England is synonymous with Christmas for tourists from warmer climes such as the Mediterranean, Asia and the Middle East. Just because tourists happen to visit once a year, and in August at that, why should it preclude them from snapping up some English Christmas goodies, too? Selfridges and Harrods view themselves as tourist meccas. So opening Christmas shops now makes shrewd economic sense because London is packed with tourists, all packing cash. It's particularly true of Arabs, who flock here in the hottest British month to avoid the far hotter summer meltdown in the Middle East, where temperatures can hit 50 degrees. Why not have a little trip to Santa's grotto to help cool them down and heat up the tills? Other shops have long since realised that August is 'Arab month'. Now is the prime time for upmarket, West End fashion stores to tailor window displays to entice the notoriously ostentatious Arabs, exhibiting more gaudy and exotic wares. As Londoners, sipping our pints and Pimms outdoors in the early evening sun off Oxford Street, we can't really fathom the mindset of tourists who buy Christmas decorations in August. You'd never catch us doing that. Then, in walks Angela, a friend who works at BBC Publishing. She's had a little bit too much to drink at her Christmas lunch at Claridges. 'Christmas lunch?' I ask. 'In August?' She replies: 'Why not? It's the month ad sales staff schmooze clients for Christmas advertising, so why not have a Christmas lunch to get them in the mood?' Why not, indeed. Pass the mince pies.