Green’s Dictionary of Slang

(orig. US) a rich young man given to much public exhibitionism, drunkenness and similar anti-social activities, all based on an excess of snobbish self-esteem; also attrib.; thus fem. hooray Henrietta.

1938		D. Runyon ‘Tight Shoes’ in Runyon on Broadway (1954) 468: He is without doubt strictly a Hoorah Henry, and he is generally figured as nothing but a lob.
1942		P. Larkin letter 12 Aug. in Thwaite Sel. Letters (1992) 41: The henries particularly amused me.
1959		C. MacInnes Absolute Beginners 76: Well, who cares? That garden party’s for the ooblies and the hooray henries, anyway.
1965		G. Melly Owning Up (1974) 21: He had decided we were ‘hoorays’ — that is, public-school jazz fans, an expression he himself had discovered in a short story of Damon Runyon’s.
1971		T. Lewis Plender [ebook] The Ferry Boat was full of Hoo-ray Henrys. [...] The kind of local the Hoo-rays referred to as Their Little Pub on the River.
1980		A. Payne ‘All Mod Cons’ Minder [TV script] 18: Bowing and scraping to all those hooray henrys.
1986		R.G. Barrett Godson 21: ‘[H]e’s now turned into a shocking Hooray Henry’.
1999		N. Cohn Yes We have No 200: The Hooray Henrys with their beepers and beamers.
1999		Observer Screen 1 Aug. 20: Georgia’s hooray friends.
2000		Indep. 21 June 3: A proper Hooray Henrietta passed by.
2004		M. Heatley John Peel 30: Hooray Henrys [...] and Merseyside moptops most certainly didn’t belong together.
2006		D. Mitchell Black Swan Green 369: Dad called Yasmin Morton-Bagot a Hooray Henrietta once.
2018		Twitter 12 July 🌐 London’s only no-go areas are the ones where pop-up VietnaMoroccan cocktail-and-taco vans run by Henrys who went to Charterhouse outnumber the humans.
2022		Twitter 28 Feb. 🌐 A grinning rah in a polo shirt walks past shouting, ‘Down with Putin! Down with Putin.’ Proximity to Clapham means this is sadly unavoidable.