Brass instruments have been used by the British Royalty since at least the 16th century. When King Henry VIII was ruling, he organized a tournament in celebration of his new born son. A painting of this event shows six trumpet players on horseback. This photo shows three of the trumpet players.
The man in the middle is most likely John Blanke, a black trumpeter who served as a musician for both Henry VII and Henry VIII. Perhaps before this time, and surely after, brass instruments have been used for many royal celebrations. These include births, weddings, and coronations. We don't know exactly what these trumpeters played, but we know that the royalty like to uphold traditions. The following two videos are examples of trumpet fanfares at recent Royal Weddings.
Start at 0:53.
For this next one, start at 1:00.
To me, it does not seem out of the question to think that the trumpeters depicted in the painting from Henry VIII's time would have played something similar to the fanfares in these videos.
As I was searching for information, I came across the Westminster Abbey website. They explain how during a coronation service a fanfare is sounded just after the crown has been placed on the head of the Sovereign. In addition, every coronation ceremony since that of George II in 1727 has used Handel's "Zadok the Priest." This piece includes 3 trumpets. Isn't is possible that these same trumpets played a fanfare? Also, this is Handel's version of the piece. According to the Westminster Abbey website, the words have been sung at every coronation sing King Edgar in 973. Perhaps Handel wasn't the first to use trumpets along with this text. As for now, I haven't found any other information but it would be interesting to study. Although this is not a brass ensemble piece, we can still listen and imagine how the trumpet was used in the history of British royalty.
Here is a link to a video with the piece. It is not able to embed on this blog. Also, the trumpets at the beginning are not part of the actual piece.