“When you’re in a hole, stop digging” (First Law of Holes)

There’s a “law of holes” rule when someone (such as a politician) gets into trouble: “When you’re in a hole, stop digging.” In other words, don’t get yourself into more trouble. Denis Healey, a British Labour politician, presented this “first law of holes” by at least 1983 and possibly coined the law.
   
   
Answers.com
Proverbs: When you are in a hole, stop digging
It is a good thing to follow the first law of holes; if you are in one, stop digging.
[1988 D. Healey Observer in J. Care (ed.) Sayings of the Eighties]
When you’re in a hole, stop digging.
[1989 U.S. News & World Report 23 Jan. CVI. iii. 46 (headline)]
William Hague seems to have forgotten the first rule of politics: when you are in a hole, stop digging.
[1997 Times 15 Sept. 1]
Parliament would be unwise to hand to somebody in Tehran, Lambeth Palace or Salt Lake City the power, by pronouncing something hateful, to create an offence under English law. You’re in a hole, Home Secretary. Stop digging.
[2001 Spectator 1 Dec. 32]
   
Wikipedia: Denis Healey
Denis Winston Healey, Baron Healey CH, MBE, PC (born 30 August 1917) is an British Labour politician, who served as Secretary of State for Defence from 1964 to 1970 and Chancellor of the Exchequer from 1974 to 1979.
       
Google Books
Parliamentary debates: Official report, Volume 44
By Great Britain. Parliament. House of Commons
Contains the 4th session of the 28th Parliament through the session of the Parliament.
v. 44 - 1983
Pg. 472:
The first law of holes is that when one is in a hole one should stop digging. That is precisely what the world should do in the present arms race crisis.
   
15 November 1983, Los Angeles (CA) Times, “Let’s Delay the Missile Deployment” by Edward J. Markey, pt. II, pg. C7:
Denis Healey, the former British defense minister, has what he calls the first law of holes: “When you are in one, stop digging.”
   
11 September 1984, New York (NY) Times, “Neogitate with Moscow, not ourselves” by Nicholas F. Brady, pg. A31, col. 2:
There is a Law of Holes that says, when you are in one, stop digging. This is a law Congress finds it almost impossible to observe when it acts on defense and arms control issues. Congress dug a deep hole for itself last summer when it failed to reach ...
   
17 September 1984, Lexington (KY) Herald-Leader, pg. A9:
“There is a Law of Holes that says, when you are in one, stop digging.”