I found the original design for this panel in the archives of the V&A.
It was by my grandfather James Hogan RDI (1883_1948) who worked for James Powell all his life.
I would like to thank Dr. Dennis Hadley for his lists of Opus sectile, which show the locations of many of the production pieces by James Powell.
The original cost of the panel was £250
http://www.tilesoc.org.uk/powell.htm