While the familiar post-1799 infantry jacket didn’t allow for much in the way of variation, the immediately preceding transition period, as the long coat morphed by stages into the jacket, was far more fruitful.
Here’s [left] a rather beautiful watercolour (attributed to Henry Eldridge) of an unidentified field officer of the Leeds Volunteers in the late 1790’s, from the collection of Leeds Museum. [Click to enlarge images.] The huge, plastron-like effect of the unusual lapels, with their buttons in threes, is quite a step forward from the orthodox parallel lapels with paired buttons originally worn by the Leeds regiment. The same flamboyant coat, but now cut to allow the lapels to button over in the mode of the time, is shown [right] in the 1802 portrait of Colonel Thomas Lloyd of Leeds (once at York Castle but now in the National Army Museum). Why buttons in threes? I’ve no idea.
But the Leeds Volunteers were not the originators of the style. Here is exactly the same style of coat but faced in green, and a companion jacket, both belonging to an officer of the 1st West York Militia, probably Captain Howard of the light company. Both are now in the Wade Collection of the National Trust, together with a matching red waistcoat with buttons in threes. A portrait [below], attributed to John Downman, of a company officer of the West Yorks around 1800 or soon after shows the same coat buttoned over. But from where the West Riding Militia derived the style, or if it was ever adopted by any other unit, I do not know.
Though here [below] is something else not too distant – a showy style of lapel worn in the late ‘nineties by both regiments of Gloucester Militia, and described in the Pearse tailors’ books as “Broad at top slanting off at bottom”.