This officer of the 1st Guards (later the Grenadier Guards) wears the laced coat worn on state occasions. These coats were worn in earlier years by many officers, but not in the Foot Guards. They seem to have been a form of court dress. Nevertheless, by 1790 their use seems to have been confined to the Household troops, and each regiment of Foot Guards had a coat like this, with regimental differences, for use on state occasions. The details shown in the plate come from a coat which is known to have belonged to an officer of the 1st Guards which is the forerunner of those worn in 1820, which was almost identical with one worn by the Duke of Wellington as Colonel of the Grenadier Guards. The uniform shown in this picture has probably never been surpassed for restrained elegance.
Sources: Coat in the National Army Museum, and a contemporary print by Dayes.