The Employment Equality (Age) Regulations [1] made age discrimination illegal beginning in 2006. Before that it was not illegal. The 2010 act, among other things, extended protection for age discrimination to other people such as prospective employees.

I'm British, and the fact that we only got around to this in 2006 seems to me to be fairly shameful.

[1] http://en.wikipedia.org/wiki/Employment_Equality_(Age)_Regul...