This refers to the Vagina of Margaret Thatcher (Former Prime Minister of the UK). The nick name for her flacid genetalia, comes ironically (HA!) from the nick name associated with her stubborness in politics "The Iron Lady".
However the nick name became cemented in the hearts of the public, when a photographer accidentally fell over and took a picture upskirt revealing her vagina to be actually made from 18th century pig iron.
This has opened up a large debate which spans many topics.
Biology - How?
Philosophy - Why?
and Politics - ......
Some have suggested that it was not her vagina at all, but a form of securtiy device to stop unwanted vermin from nesting in there. However regardless, the media splash was enough to concrete in the term Iron Beef Curtains.
I would like to be the first, then, to suggest, that instead of wasting, millions of pounds of taxpayers money on her state funeral. We should instead, recycle her Iron Beef Curtains.