In terms of protocol, President Trump did nothing inappropriate in walking in front of the Queen, and I am sure it was just a result of him having much longer legs than she did.
British protocol treats the President of the United States as the King of a friendly nation (it’s an old protocol and hasn’t fully come to terms with republicanism).
And, once again, there is a fundamental principle that offence is only taken if it is intended. The Queen would not have been offended by this, even if he had made a minor gaffe.
Do the same ones carry the coffin throughout the whole “process” during the week, or do they change?
Adhering to that simple principle would put most of the Left's political initiatives out of business. :)