The faders on BBC mixing desks customarily work in the opposite direction to other desks. You push the fader away from you to get quieter and pull towards you to get louder. This can obviously cause confusion for people working in more than one radio station.

Originally, all mixers were in the up-is-quieter format, with the SSL 4000E probably being the first to reverse the trend. While other manufacturers followed the 'new way', the BBC still have some examples of the older form.

The traditional (and possibly accurate) reason given for this is that if the presenter falls asleep on the job and slumps forward, they will effectively mute the output, rather than blowing everyone's ears off.


Source:
http://www.studio-sound.com/archive/july99/celeb_mix.html