Can you help The Postcard Detective

When a farm has a printed postcard made of it one expects it to be important enough to be easy to trace. A search of trade directories has drawn a blank on this one, and the only relevant reference to "Yew Tree Farm" found in a google search was to an extract from The Protected Valley which read "There were two farmers at Green End in 1841 – George Mardell at Green End Farm, who employed three men and a woman, and William Gardner at Yew Tree Farm."

Was it another name for Libury Hall Farm? It does not seem to be part of Gernan establishment (see Libury Hall, Little Munden, early 20th century).

Interestingly the back has three portraits stuck on it - Dudley 10½, Clive 8. and Richard 6, and the date August 1921. Were these the children of the person living in the farm in 1921?

Can you identify the family?