The voice behind KITT

While starring in St. Elsewhere, William also voiced the iconic car KITT in 1982's Knight Rider.

Ignoring instructions to sound robotic, he used his natural voice instead.

He later shared on his website: "I was amazed when NBC bought the series and they asked me to be the car.

"But it was a nice extra paycheck that would take little time from my main job at St. Elsewhere.

"I took no billing and figured no one would know. I was wrong.

"Thirty years later people are still recognizing my voice as that of the Trans Am on Knight Rider."