The Avengers: Season 2, Episode 13
“Death Dispatch”
Filming begins: 22-Jun-62
Filming completed: 23-Jun-62
Released London: 22-Dec-62
http://www.dissolute.com.au/avweb/season2/213.html
This was the 4th episode shot for season 2. Most were shot within a month of broadcast. It was the first episode filmed with Honor Blackman as Cathy Gale.
http://www.dissolute.com.au/avweb/season2/index.html
The Sunday Night Playhouse would have been on a much tighter schedule because they broadcast every week of the year.
That makes sense. Now to find out how BBC “discovered” her and what she was doing where at the time BBC discovered her prior to these TV roles. They usually pick actresses who attend prestigious London acting schools and have performed successfully in London theater and are reliable actresses.