Time Is Incorrect On Windows 7 X64?

The time on my win 7 x64 ultimate is incorrect. I am in the uk so am on London time. We have recently entered Daylight Saving Time. So the clock should have gone back one hour but it appears to have gone back two! A week ago the time of day now would have been 00:20, the time now should be 23:20 and the time my clock is showing is 22:20. I have looked in control panel > Clock Language Region - and my time zone is set correctly to UTC Dublin Edinburgh Lisbon London as it should be. I try unticking adjust for daylight saving time and click apply but this doesn't even change the time( not even by one hour as it should) it seems to not matter whether it is ticked or unticked, my clock remains an hour behind what the current time actually should be.