Dehns' client Qual-Chem Ltd was a small, family run business supplying services and materials to the steel industry. When steel is made, a substance called slag is formed on the surface of the ladle in which the steel is formed. This slag has be "killed" and removed during the steel making process as this substance spoils the steel below.

Dehns' assisted Qual-Chem in patenting a new process for killing slag in the steel making process securing protection in the UK and Europe for their invention. The innovative process significantly reduced the amount of spoilt steel.

On behalf of Corus, Qual Chem carried out the patented process in the Corus steel factory in South Wales. In a cost saving measure however, Corus chose to start carrying out the patented process themselves. With the help of solicitors and barristers who agreed to work for a contingency fee, Qual-Chem sued Corus for the infringement of its UK patent in the High Court. Qual-Chem were able to prove to the Court that their patent was valid and infringed. Corus appealed that judgement but the verdict was upheld. The Appeal Court Judge, Jacob LJ, even felt able to dismiss the Appeal without hearing argument from Qual-Chem.

This David and Goliath story shows that even a small, family run business can take on the might of a multinational conglomerate if they have a patent.