RECORD prices always send a shockwave through the world of antiques, and none more so than a few weeks ago when a new price record was set for the sale of a single postcard. That price was £31,750!

The reason for this truly exceptional price was that this picture postcard dated from the year 1840, and -- so far at least -- is the earliest one to have been discovered.

It therefore had very special collecting interest, which was reflected in its amazing price when sold at auction.

The card was postmarked in London and sent to a well-known author of the period, and its discovery has caused the history of the postcard to be rewritten, for it has always been thought that the picture postcard was not invented until the 1870s.

Certainly it was around that time that they began to gain some popularity on the continent, particularly in France, Austria and Germany, but it was really the 1890s before Britain caught on to the postcard boom, and the great heyday of the picture postcard was actually the Edwardian period from around 1900 until the outbreak of the First World War.

In the days before the widespread availability of the telephone, the postcard was the cheapest form of mass communication and the postal system so efficient that you could post a card in the morning making an appointment to have tea with a friend that same afternoon and be fairly sure the friend would get the postcard in time to keep the appointment!

This freak price for a picture post card has refocused public interest on the value of old post cards generally.

I have written on this subject once or twice in recent years, usually concentrating on a specific collecting genre such as comic postcards.

More generally, most picture postcards tend to be priced from about 30p upwards at antiques and collectors' fairs and 50p would be a fairly typical price, though what really determines the value of an old postcard is not its age or where it was posted or even the message -- it is what the picture actually shows.

On the whole, greetings cards, landscape scenes and pictures of public buildings such as churches and town halls have the least value because they are least collected. However certain categories of postcard are collected, and values can move up quite considerably often to several pounds per card.

Subjects such as sport, transport, and domestic street scenes tend to be among the most sought after of the photographic cards.

But there is also strong demand for "artist drawn" postcards where the picture was originally created by an artist rather than a photographer.

Certain artists are more collectable than others, and prices can be anything from £5 to as much as £100 for very desirable artists such as Raphael Kirchner and Alphonse Mucha.

Between those extremes there are literally hundreds of different sub-categories of collecting, with some people concentrating on postcards which purely show, for instance, teddy bears or dogs, actresses or railway engines.

Any one who has a bundle of old postcards in the attic should get them checked out by an expert.

Most auctioneers will offer free advice on values, and there are a number of postcard price guides available in the bookshops.

Mostly, you will probably find that your postcards are worth just a few pence, but you never know -- there could be another 1840 postcard out there just waiting to be found!