While on my trip in the UK, I noticed a staggering amount of armed police officers guarding the gates to castles and palaces. These were not security guards but actual police officers. All were armed with Glocks and a couple of them were armed with either a MP5 or MP7, and this was at every place I went to.

This is at Windsor Castle. This gate is the exit for tourists. However it is a controlled entrance for certain vehicles. It is guarded by a couple of officers, one of which is armed with a MP5A4 with Surefire fore end.

Here is a another gate at Windsor Castle and this officer is carrying a MP5A5. 

This is the gate guarding Whitehall in London. Again we see they are issued Glocks and MP5s.

This guard is different. All the other guards I have seen wore white short sleeves but this guy has black long sleeves. And he is armed with a H&K MP7! He was just standing on the sidewalk in front of the Horse Guards in London.

Edit: A reader noticed that this MP7 does not go to 11. It is semi-auto only. Also I just noticed that the iron sights are like that of a MP5 style. Not the standard folding MP7 dual function irons that I usually see.