c. 1961, part of set to commemorate the "Centenary of Post Office Savings Bank"
designed by Michael Goaman
The profile of Queen Elizabeth II seen on the above stamp incorporates a portrait by photographer Dorothy Wilding.
Using a photographic approach presented difficulties for future commemorative postage stamp designs. In 1966, as result of a compromise designed by David Gentelman, the Queen’s head was simplified to a cameo silhouette (based off of Mary Gillick’s earlier effigy design). But in 1967, sculptor Arnold Machin was commissioned to create a new representation of the Queen which became a classic. The evolution of the design is very complex, with political involvement making it tricky.
The design history involving mandates and strict style guides for Queen Elizabeth II's depiction on UK stamps recently became of extra interest following a court battle which presented a possibility of removing Queen Elizabeth II’s cameo in future postage stamps.
I'm not too informed on the British monarchy and its influence on stamp designs. I'll need to read up more about it, and will probably make a better post once I gather some more info.