What is a British ceremonial military hat called?

Busby was the name of a large round fur hat that was not very tall, such as the French cavalry in the Napoleonic War. The Bearskin hat was a tall fur hat worn by grenadier infantry of the many countries during the Napoleonic War. IT was also called the Busby. Today you can see it being worn by the British Palace Guards while on duty and on parade. "Ushanka" was the name of the Russian fur hat that was worn by their soldiers under their helmets or alone. Fancier designs were worn by Russian generals. They looked like the hat common among Cossacks.