Everybody should follow the Law but I strongly doubt that HM the Queen could be even in theory stopped and searched, that mrs.May and members of HMG could be stopped and searched (being randomly selected).
Diplomats can not be stopped and searched anyway.
I mean that there are exceptions. Official guest of British Parliament is not just a random stranger. His treatment should be different, respectful - if you understand what do I mean.
Sadly for your agenda the police here couldn't care less about the Russian you keep mentioning over and over. He's a 'nobody' and of no importance whatsoever, so was no less likely to be stopped and searched that anyone else fitting the criteria to be stopped and searched. Lots of people are guests in parliament everyday, he was no different.
You may feel this Russian was somehow different to anyone else in the area, but that's just pro Russian delusion.
As for you silly attempt to bring the queen into this, you will have heard and seen that her husband The Duke of Edinburgh was recently involved in a car crash. He and the other driver were both breathylised, and both treated the same by the police.
I fully realise you want to divert from this latest Russian erosion of freedom, but pretending a 45 second stop and search in the uk is anything like being bundled into a police can and removed from the streets like happens in your own country but it is a very weak effort on your part.