I would concurr Alan,
this is taken from the MGOC website
...The first cars known MGs were in fact special bodied Morris Cowleys. Old Number One was first seen at the 1925 Lands End Trial. Cecil Kimber had the car specially built to compete in the trial and this was indeed based on a bullnose Morris Cowley chassis.
Which suggests there were previous cars known as MG's, however Old No. 1 was first MG sports car to display the MG Octagonal badge....apparently
Maybe that is a more accurate sentence than it being the first Sports car, although would you actually call those first Morris MG's sports cars????
I know nothing, just read and plagiarise from the Tinternet