There is a law in London (all of Great Britain) that the fireproof curtain MUST be seen by the audience to work sometime during each performance. So down and up it comes, usually at intermission - not that I'd know, I've always had a weak bladder. And most theatres have wonderful velour house curtains that date back decades. The "Royal" houses (Drury Lane, Theatre Royal Haymarket and The Royal Opera have the crown emblazonned on the curtains. These curtains are heavy as hell and used to take four or five guys to raise/lower.
http://www.broadwayworld.com/board/readmessage.cfm?thread=972787#3631451
http://www.broadwayworld.com/board/readmessage.cfm?thread=963561#3533883
http://www.broadwayworld.com/board/readmessage.cfm?thread=955158#3440952
http://www.broadwayworld.com/board/readmessage.cfm?thread=954269#3427915
http://www.broadwayworld.com/board/readmessage.cfm?thread=955012#3441622
http://www.broadwayworld.com/board/readmessage.cfm?thread=954344#3428699