Deb's delight

A "deb's delight" was something Ben Jackson claimed he wasn't when Polly Wright — whom he had only just met — invited him to lunch at the Post Office Tower. Polly responded by regarding him in his HMS Teazer cap and uniform, happily smiling, and saying, "I can see that." (TV: The War Machines)

Behind the scenes
In context, the remark reinforced one of the central aspects of their relationship: her upper class breeding — which he usually highlighted by calling her "Duchess" — and his working class life as a sailor. Though undefined in episode 2 of The War Machines, its usage squares with the of a single, successful, well-bred man that would be attractive to a debutante.