Each February, the upmarket Swiss ski resort of St Moritz hosts a series of unique horse races on a frozen lake - the sport, known as 'skijoring', and has existed for over a hundred years.

On the frozen ice of Lake St Moritz in western Switzerland, the scene looks something like a roman chariot race, in the snow.

But this is in fact skijoring. On the first three Sundays in February, thousands turn out to watch thoroughbreds from around the world pull skiers around a 2700-metre track.

Reaching speeds of up to fifty kilometres per hour, it's a unique experience for both horses and jockeys.

"It's certainly something very unusual. It only exists in St Moritz. It's almost impossible to describe what you feel while you're racing, but it's definitely something special. We've been doing this for years and we're not stopping," said Skijoring jockey Franco Moro.

The races are part of the White Turf meeting - Switzerland's most lucrative equestrian event.

For well-heeled spectators, it's a good chance to quaff champagne and oysters as well as enjoying the wintery sport - though not everyone seems entirely convinced...

As for the horses, they're equipped with special shoes, and jockeys say most have no problem running on the ice.

"Some horses adapt well to the snow - others not at all. You have to try. It's difficult to say in advance whether the snow will suit them. All you can do is try. Ninety percent of those which run on grass can also run on the snow. It just takes a bit more strength," added 'White Turf' farrier Christian Lampert

Skijoring was invented in St Moritz more than a hundred years ago.

Calling for strength, skill - and not a little courage - the races look set to remain a key date in Switzerland's social calendar.