Pupils in Coventry will be helping to launch the first ever heat-sensitive stamp next week as the Royal Mail celebrates a national obsession.

The set of stamps with a weather-theme will be launched by pupils from Bablake School, which runs a weather station in Coventry.

As quick as the British weather changes, so does the colour of the cloud on the first class stamp.

A small section of the stamp has been printed with thermochromic ink which sees the cloud change from dark and gloomy to a cheerful sky blue when it is touched.

Rubbing the innovative stamp with a finger heats the paper and activates the ink, changing the colour.

Mark Thomson, Managing Director, Royal Mail stamps and collectibles, said:

"Our stamps are always visually interesting, but with the weather set we are also appealing to people's sense of touch. Just by rubbing the first class stamp you can change the weather. If only it was that easy in real life!

"We feel the stamps capture the wide range of weather conditions we enjoy and endure in Britain; from tumbling cats and dogs in the rain on the second class stamp to butterflies and birds relishing warmer conditions on the 65p stamp.

"Each stamp is actually a segment of one complete image, bringing all four together creates the dial of a barometer, which for generations was a feature in homes up and down the country.

"We are issuing this complete image as a special miniature sheet which we are expecting to be very popular as a novel gift - whatever the weather."

The Bablake pupils will be joined by Coventry postal workers to pose with large scale blow ups of the stamps at Bablake Weather Station at the school playing fields in Coundon.

The station was established at the school in 1977 by Steve Jackson, who is now head of Geography.

The weather station is now fully computerised, conforms to Meteorological Office standards, and has a number of regular subscribers who receive weather data on a weekly and monthly basis.