By James Cove BBC News

At the beginning of the last century old skiing posters would be hung on railway stations, free if only you could peel them off the wall.

Today they can command up to �20,000 and their price is rising.

They are a serious investment for collectors, made even more attractive in these times of falling stock markets and economic uncertainties.

The St Moritz ski bunny is up for grabs

This week in London, Christie's holds its annual auction of ski posters and memorabilia. And it is a market on the rise.

It is the only auction house in the world to hold such a sale and it is expected to realise in excess of �250,000.

"These art deco ski posters are really taking off in popularity," Nicolette White, Christie's poster specialist, told BBC News Online.

Multiplying value

"Skiers are passionate about their sport and they want to own a bit of its history".

Three years ago the poster of the Palace Hotel in St Moritz had an asking price of �2,000, but in this week's sale it is listed at �7,000 - not a bad return on your investment.

This poster was originally an advert for Air India

Last year a 1917 poster of Davos fetched an incredible �17,625.

Many of the poster date from the 1920s and 1930s and they hark back to the first days of mass ski tourism.

Then, as winter sports holidays became a viable option for many, the railways and resorts commissioned some of the finest artists of the day to create the posters to encourage people to visit The Alps.

Holiday hopes

The artists to look for are Roger Broder, Emil Cardinaux and Paul Ordner.

This 1930 poster should fetch up to �3,000

Today the most popular posters are those from the traditional ski resorts with a dedicated following - Chamonix, Wengen Gstaad, Davos and St Moritz.

Olympic ones always command a premium and any that are unusual like the St Moritz bunny can be valuable.

Action ones like Sports d'Hiver dans les Vosges also attract special interest.

The sale will see collectors from all over the world.

There may also be a few enthusiasts who want to buy a poster now and head off for a holiday in a few year's time on the profit they hope to make.