Master of the Horse is an official position in several European nations. It was more common when most countries in Europe were monarchies, and is of varying prominence today.
Lord Vestey, Master of the Horse from 1999 to 2018, riding to the Queen's Birthday Parade in 2012
Lord de Mauley as Master of the Horse during the coronation of Charles III in 2023
Marcus Aemilius Lepidus was a Roman general and statesman who formed the Second Triumvirate alongside Octavian and Mark Antony during the final years of the Roman Republic. Lepidus had previously been a close ally of Julius Caesar. He was also the last pontifex maximus before the Roman Empire, and (presumably) the last interrex and magister equitum to hold military command.
Denarius of 42 BC depicting Lepidus, age about 57. The inscription is III vir rei publicae c(onstituendae) Lepidus pont(ifex) max(imus), meaning "triumvir for the regulation of the republic, Lepidus, Pontifex Maximus".
Aureus of Lepidus, c. 42 BC
Lepidus (right) browbeaten by Antony and Octavian. Illustration to Shakespeare's Julius Caesar by H. C. Selous.