Episode #15, "The Frighteners" was long thought to be the sole surviving episode of the first season. The other 25 episodes made in 1961 were believed to be lost forever as a number of episodes were broadcast live. However, in 2001, the 1961 episode, Girl on the Trapeze (1961), was discovered in the United States (odd considering the first season wasn't sold abroad; the first 15 minutes of the very first episode, Hot Snow (1961), were also found at this time, both within the UCLA archive), whilst a print of Tunnel of Fear (1961) surfaced in 2016.
This episode from the 1961 series, is one out of two in existence that features both Keel and Steed.
From the 1961 episodes until 1965, very little was divulged about Steed's background. He was presented as being more of a shadowy character.
Steed isn't wearing his trademark bowler hat.
Ingrid Hafner didn't return for the next series. Her character was permanently written out.