Joseph Fiala (c1748--1816) was a famous Czech composer and performer of his day. Mozart spoke highly of him, and he held a succession of important musical posts at European courts. His Divertimento in D is a recent discovery, and is published here for the first time. Written for the 'Klappentrompete' (Keyed Trumpet), it dates from the same period as Haydn's Concerto in E-flat for the same instrument, and represents a welcome (and technically less demanding) addition to the classical Trumpet repertory.