Why is Mr. Birling impressed with Gerald?

Mr. Birling's an inveterate social climber. Although he's amassed fantastic wealth, he still feels a slight twinge of inferiority on account of his humble origins. More than anything else, he craves social respectability in the eyes of the aristocracy. And this is where Gerald fits in. Gerald is a polished young man from an elite, old money background. Mr. Birling is excited at the prospect of his daughter's impending marriage to the son of Lord and Lady Croft. This will mean the uniting of two great families, old money and new. The forthcoming marriage represents a good deal for both families: Gerald Croft will marry into money, whereas Sheila Birling will burnish the good name of her family with the luster of noble lineage. No wonder her father's so impressed with his prospective son-in-law.