Green’s Dictionary of Slang

1. the police; occas. a police officer; thus Bill from the Hill, officers serving at Notting Hill police station in London W11 (cf. Bill, the n.).

1895		Mirror of Life 28 Dec. 11/2: [A] change came o'er the scene when the ‘blues’ put in an appearance (perhaps one of old Bill's favourite ruses).
[1925		N. Lucas Autobiog. of a Thief 248: A principal warder, whom we called ‘Old Bill’ – for obvious reasons].
1958		F. Norman Bang To Rights 138: Two Old Bill’s came up to me and told me they had a warrant for my arrest.
1962		R. Cook Crust on its Uppers 26: As for Old Bill, the law, who can’t leave us alone [...] he’s a groove behind.
1970		G.F. Newman Sir, You Bastard 61: I always run when Old Bill’s around.
1977		D. Powis Signs of Crime 173: Bill, or Old Bill Specifically, the Metropolitan Police and, generally, all police: ‘Is he Bill?’ means ‘Is he a police officer?’.
1979		K. Bonfiglioli After You with the Pistol (1991) 332: Every [...] professional team of thieves has a [...] ‘lighthouse’. [...] He has but one simple, God-given skill: he can recognize ‘fuzz’, ‘filth, ‘Old Bill’ or any other form of copper, however plainly-clothed.
1983		A. Payne ‘Get Daley!’ Minder [TV script] 40: The old bill were crawling all over the warehouse till nine tonight.
1984		B. Ellem Doing Time 193: old bill: police.
1986		R. Hewitt White Talk Black Talk 87: The Old Bill come over, pushed the blokes away. What did ’e do? Nicked the black bloke for causin’ trouble.
1989		in G. Tremlett Little Legs 3: The Old Bill came round to get him.
1996		P. Howard The Joy (2015) [ebook] Old Bill decided to clamp down on inner city crime.
1999		Observer Mag. 30 May 16: I did get a bit touchy when the Old Bill started pounding on the door.
2007		N. ‘Razor’ Smith Raiders 2: The last thing you want is [...] armed Old Bill on their way.
2011		J.J. Connolly Viva La Madness 34: Nobody, not his relatives, business associates or British Old Bill could get those funds.
2013		Telegraph on line 16 Jan. 🌐 It was murder — all you could hear was Old Bill flying round all over the place.
2021		Breen & Conlon Hitmen 226: ‘The Old Bill, watching to see who you’re meeting [...] all that shit’.

2. the police force as an institution.

1981		J. Sullivan ‘Big Brother’ Only Fools and Horses [TV script] I mean you can’t trust the Old Bill can you!
1992		I. Rankin Wolfman 58: Know why we’re called the Old Bill? [...] Some say it’s because we’re named after a certain London landmark.
1995		J. Cameron Vinnie Got Blown Away 1: Belled 999 on the mobile. Operator came on asking what service. ‘Old Bill,’ I goes.