I spoke to one of the security staff at LHR this week about this change and he informed me it was as a result of a visit by some auditing body from the EU regarding airport safety.
He preceded to tell me it was common all over Europe (obviously this is what he had been told), I pointed out that I have only ever seen this in the USA and Germany, everywhere else I currently fly to and from do not enforce this.
The chap told me all EU airports are supposed to be implementing this change at sometime in the near future.
I have my theories as to why this is necessary (and therefore a good thing) but for obvious reasons will not post here.
Bad Attitude