[foofoo55]

The Guardian article claims "Sinclair invented the pocket calculator", but other calculators were on the market before his:

http://www.vintagecalculators.com/html/history_of_electronic...

[edit] More details on his calculators, which were quite cool, especially his trick to decrease power consumption and the super-slim Sinclair Sovereign:

http://www.vintagecalculators.com/html/sinclair_-_the_pocket...