[The first 30 pages of Muirhead’s Guide to London, 1928](http://www.boingboing.net/2007/11/18/muirheads-london-gui.html).
Interestingly, the guide suggests tipping of 20 per cent, which is quite a bit more than the [current suggestion for London](http://en.wikipedia.org/wiki/Tipping_by_region#United_Kingdom). So perhaps the direction of tipping is not all in one direction as it sometimes seems.