The 150-strong herd, the only one of its kind in Britain, spends most of the year out on the Scottish moors. Every November, however, part of the herd embarks on a tour of the country's shopping centres, a fund-raising venture which helps pay for its keep. As well as shopping malls, where they attract crowds of 10,000, the teams make seasonal visits to hospitals and old people's homes.
A reindeer indoors is not as daunting as it sounds; these creatures are smaller in real life than most illustrations might lead you to expect, though their antlers are just as impressive. Even when they don't match. Frustratingly, Christmas coincides with the antler-dropping season, when the males cast this year's set in preparation for next spring's new growth.
"I've had many a heartache about a Christmas reindeer losing his antlers at the worst possible moment," says Tilly Smith, who owns the herd with her husband Alan. "There have been times when we've had to harness up two reindeer with only one antler each - one on the left and the other on the right - in a desperate attempt to make them look like a normal pair."
The antler problem is one reason for making sure there is a second pair of animals at each venue. The two best lookers are harnessed to the specially made sleigh with the "spare wheels" and the calf trotting along behind.
Do the reindeer get overheated in the confines of a centrally heated shopping centre? Tilly Smith explains: "They have no problem in normal outside temperatures down south, although we have to be a bit careful of them getting hot indoors because of their big thick coats. But in fact at most of the events they stand around outside, or near the doors. We also rotate them, if they look a bit hot."
But how do they manage without the lichen, heather, sedges and blaeberries which they graze on out on the hills? "We give them a mix of sugar beet, oats and barley, and we always bring some lichen with us just to keep the smile on their faces," says Tilly.
How does one come by a reindeer herd? The Smith's Reindeer Company is the result of a management buy-out. Alan was the herdsman, Tilly a volunteer post-grad zoologist with whom he fell in love. When the herd's founders, Mikel Utsi and his wife, died, the couple decided they knew the herd well enough to take it on themselves. From a pack of 90 they have increased numbers to 150, partly though a gift from France of 38 and another 10 from "Santa Claus, the Movie" and partly through successful breeding.
Reindeer are extremely hardy, say the Smiths, they do not damage their environment, and they ignore other browsers. Which makes them ideal visitors to the average pre-Christmas shopping mall.
'Velvet Antlers, Velvet Noses' is Tilly Smith's account of her life with the reindeer herd (Hodder & Stoughton, pounds 14.99).
For further details of the reindeer tours contact: The Cairngorms Reindeer Centre, Reindeer House, Glenmore, Aviemore, Invernesshire PH22 1QU (01479 861228).