Green’s Dictionary of Slang

1. pleasing, admirable; also as adv., perfectly.

1855		T. Haliburton Nature and Human Nature I 27: Well, they fell into the trap beautiful.
1862		‘Cheap John’ in Prince of Wales’ Own Song Book 50: Next article is a marvellous go-a-head fishing rod [...] It gets the finny tribe in a line beautiful, and regular strings ’em to rights – with a hook.
1909		Sun. Times (Perth) 26 Dec. 15/11s/1: For a man who calls himself an ‘Australian born businessman’ the blunder was beautiful!
1911		E. Ferber Dawn O’Hara (1925) 32: Well, Dawn, you’ve made a beautiful mess of it. A smashed-up wreck at twenty-eight!
1926		Breton & Bevir Adventures of Mrs. May 152: ’E looked beautiful creepy, and Em were quite proud of ’im.
1965		C. Brown Manchild in the Promised Land (1969) 87: Nick was the most beautiful cat up at Wiltwyck.
1968		L. Wolf Voices from the Love Generation 49: First of all heroin is bea-u-tiful.
1971		J. Mandelkau Buttons 42: We had a beautiful time.

2. happy, satisfied.

1971

T. Thackrey Thief 16: They’d stuck to the rules, the way I wrote them. Beautiful.

3. clever, shrewd, also used iron.

1981

J. Sullivan ‘Big Brother’ Only Fools and Horses [TV script] A financial adviser? Bonjour Trieste, you are beautiful, you are Rodney!