It probably helped that Birley's background included Harrow (where Churchill attended) and Trinity College, Cambridge, so he was socially acceptable to potential clients. His art training included some time spent at the Académie Julian in Paris.
A brief biographical note is here, and another one is here. Perhaps even more interesting than Birley are some of his descendants. For a dab of dirt on that subject, click here.
Although he was no John Singer Sargent or Philip de Laszlo, he was a competent portrait artist who delivered the anticipated goods to rich, famous, or royal clientelle. As you might notice regarding the images below, Birley usually portrayed his subjects from the knees or waist up, and left plenty of largely empty space around their heads.
A fairly early example of Birley's work.
Painted when she was a teenager. For more on the life of this Woolworth heiress, click here.
The scientist shown with some laboratory equipment.
This seems to be a posthumous portrait, as Mercier died in 1934. I include it because it shows Birley's skill at depicting human skin, not an easy matter.
When Ike was in command of NATO. One of Birley's last paintings.