David Hockney
(1971) 

The Portrait of Sir David Webster is a 1971 portrait by the English artist David Hockney of the arts administrator David Webster. It was commissioned to mark Webster's retirement as the General Administrator of the Royal Opera House in London. The portrait hung for several decades in the opera house. 
In 2020 it was put up by the Royal Opera House for auction at Christie's due to a decline in their income as a result of the COVID-19 pandemic in the United Kingdom. It sold for £12.8 million against a presale estimate of £11–18 million. It is currently in the National Portrait Gallery on long-term loan from a private collection.

https://en.wikipedia.org/wiki/Portrait_of_Sir_David_Webster

Portrait of Sir David Webster 
1971
Acrylic on canvas
152.8 x 184.5cm

Private collection, currently in the National Portrait Gallery on long-term loan.