Why are women and men both called actors now (UK)?

Women are not actresses, but (female) actors.
For example:
http://www.guardian.co.uk/stage/2009/oct/09/keria-knightley-theatre-west-end

I noticed this a while ago and wanted to know why and when it happened. It might only be a UK thing, because I've noticed in UK newspapers and BBC content. There is still an Oscar for best actress, and iMDB, Roger Ebert etc. still use the word 'actress'.
Anyway, is it part of making language more PC/less sexist/more 'equal'?

I've always used the word actor for both male and female actors. I think it just makes more sense in the modern world to have one word for both genders, since that's how it is for most other similar things. For example a female doctor is not a doctress. A female banker is not a bankeress. So to me it feels more natural to just call an actor an actor regardless of their gender. I don't think it's really a conscious effort to change the language, just something that's happening naturally.

It is simply because serious female thespians don't like the traditional connotation of the word "actress" with prostitution. It isn't particularly new at all.