“I reversed the polarity of the neutron flow.”

After “The War Games”, the sonic screwdriver wouldn’t reappear until the Season 8 story, “Colony In Space”. However this story would see the first appearance of the prop that would become the most iconic of the classic era sonic screwdriver designs. 

The new sonic screwdriver physical prop was originally kit-bashed together from reused Gerry Anderson props after his studios had a clear out. The main body was a futuristic "screwdriver"  featuring a black spiral that was used by Alan Tracy in the 1966 film, “Thunderbirds Are Go” and the emitter section was a microphone from “Captain Scarlet and the Mysterons” used by the character Captain Blue. 

Before the prop appeared as the familiar sonic screwdriver in Part 5 of the Doctor Who serial “Colony In Space”, it appeared in the same story in Part 3 as a handcuff key used by the IMC mining engineer Caldwell. This handcuff key was simply just both of the Anderson props fitted together with an added clip. When the prop appeared again as The Doctor's sonic it had been redressed with colored electrical tape, aluminum tape and paint to distinguish it from its previous form and the clip was removed. 

After its introduction the physical prop would go through multiple changes, including the emitter section being modified and the end cap having a milled angled flat added. When Pertwee’s Third Doctor regenerated, the original filming prop was revamped and carried over to the next Doctor. 

In total, this original prop that started life in 1966 for “Thunderbirds Are Go” was in continuous use as the sole sonic screwdriver prop on Doctor Who from 1971 until 1982 spanning a remarkable eleven seasons and eleven years of production. 

It is believed that the original prop was kept by producer John Nathan-Turner in his office for a number of years until it mysteriously vanished. Its whereabouts or even survival still remain unknown to this day.