Conversation so far:
What happened during the survival of At Last the 1948 show episodes?
Thames Television wiped the material once they had acquired the Rediffusion London archive, and all but two episodes were destroyed.
Did many people watch the At Last the 1948 Show compilation episodes?
What else happened during the Survival of episodes besides the destruction of At Last the 1948 Show material?
Out of an original total of 13 episodes, eleven now exist in complete or near-complete form, while two remain incomplete.

Question: Why were they incomplete?
Self-contained rewrite: Why were there incomplete At Last the 1948 Show episodes?