AAQ:
A shtadlan doesn’t have his own Torah. For example, a shtadlan can’t get baptized and live as a Christian in order to better help Jews in a royal court.
(When Shabsai Tzvi SR”Y converted to Islam to save his life, the rabbis that he fooled finally realized that he was indeed wrong. That was despite all the kiruv he did. According to you, they should not have changed their minds about him. Who cares that he converted to Islam?)
It’s sad that this even has to be stated: Hashem runs the world, and “lev melachim viSarim biYad Hashem”. Hashem obviously does not need any pompous “Chief Rabbi” to enter a Church.
LiHavdil elef havdalos, when a kohein must attend a levaya, the funeral homes have a video hook-up to a separate room right outside the funeral home so that the kohein can participate and not become tamei laMeis. The UK Palace could have (and likely would have) easily done something similar for their Chief Rabbi to help him.
Remember Rav Chaim Brisker’s line: if the Jews don’t make kiddush (as in separate from the goyim) then the goyim will make havdala. Think of the Kiddush Hashem that could and would have made, and the aivah that it would have removed! “Chief Rabbi attends coronation in a special tent put up specifically for him to accommodate his religious laws that forbid him from entering a church”. Afterwards, at the palace, or anywhere else outside the church, he could have blessed the king just like the “other faith leaders”.
In fact, we know that their king himself was willing to break protocol to have the Chief Rabbi leave before the king so the Chief Rabbi could go home for Shabbos.
This was and is a disgrace and an abomination.