Yarvelling was a famous Dalek scientist.
Under Minister Zolfian, he developed a mobile war machine for the war against the Thals. When a meteorite storm detonated the neutron bombs, Zolfian and Yarvelling survived in the war council chamber.
Two years later, they emerged from shelter to look for surviving Daleks and destroy any surviving Thals, but found the surface of Skaro to be devastated and contracted radiation sickness. They were discovered by a "machine Dalek" - a mutated Dalek survivor inhabiting the war machine Yarvelling had developed. The two old Daleks rebuilt the war factory, started a Dalek production line, and made a special casing made for the first Dalek, who declared itself the Dalek Emperor. Zolfian and Yarvelling died of radiation sickness just as the casing was completed. (COMIC: Genesis of Evil)