I was wrong about the BAA handbaggage gauges at Gatwick - here is a BBC article which includes a photo of the new gauge:
http://news.bbc.co.uk/1/hi/uk/4794489.stm
Note the clever use of medium grade mdf, I would guess that BAA must have had to wait for almost 24 hours to get these babies made and delivered??? Plenty of time to brief the staff then.