system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what are the palace guards in England trained to do?
gpt
They're active duty troops from several elite regiments (and sometimes commonwealth units), and a lot of them have extensive experience in Iraq and/or Afghanistan.  They're regular army. 

So basically they are trained to kill you if necessary, and are damned good at it. Don't test them.