The card - with a Penny Black stamp - was sent in 1840 to a writer called Theodore Hook who lived at Fulham in London.

The hammer went down at �27,000 but the total price including commission and value added tax (VAT) was �31,750.

It was bought by collector Eugene Gomberg, of Riga, Latvia, in a telephone bid at the London Stamp Exchange auction.

Posted in 1840, the hand-coloured card was addressed to "Theodore Hook Esq, Fulham", a playwright and novelist noted at the time for his "wit and drollery".

It caricatures the postal service by showing post office "scribes" sitting around an enormous inkwell.

Significant

Hook probably sent it to himself as a practical joke.

The significance of Hook's card was not realised until last year, when an expert discovered it in a stamp collection.

Until then it had been thought the postcard was invented in Austria, Germany or the United States in the 1860s.

But the card's discovery makes Hook the undisputed "postal equivalent of the Earl of Sandwich", said Mr Proud.

"It is also the only use of a Penny Black on a postcard that we have," he added.

The card and the stamp were authenticated by the British Philatelic Association.