Henry Smithers
Smithers was a scientist who developed the insecticide DN6 in the 1960s, in the hopes of ending famine, having spent a lot of time working on it.
In June 1969, he found out his business partner Forester had murdered government official Arnold Farrow to prevent his negative report on DN6 from being filed, and helped Forester cover up the murder.
Smithers turned against Forester on finding out how lethal DN6 was and disarmed the gun-wielding businessman, who had had a makeshift bomb — made from an aerosol can of insecticide ignited by a gas tap in the lab — explode in his face.
They were both arrested by PC Bert Rowse, who had been alerted to the suspicious goings-on by his telephone exchange operator wife Hilda. (TV: Planet of Giants).