London Underground classic “Way Out” sign, 1998
I think this was in Covent Garden station. This sign dates to pre-1916, since it uses a different typeface from the now-iconic one developed by Edward Johnston for the London Underground and put into use that year (http://en.wikipedia.org/wiki/Johnston_(typeface)).
The official London Underground typeface is available from http://www.p22.com/products/london.html. A free version of this typeface can be downloaded from http://www.fontstock.net/10483/london-tube.html.