Photo credit: : National Trust, Polesden Lacey
The style could be compared with that of the portraits assigned to Moscheles on Art UK. If by Moscheles, the likelihood is that the sitter is Jewish, as his clientele was predominantly Jewish.
It would be very interesting to know if this gentleman was actually Jewish, given Dame Margaret's flirtation with Nazi ideology in the years before her death in September 1942, especially in light of the planning for the Final Solution at Wansee in January of that same year. If he is Jewish, could he have held some important position in the Greville family's affections or in their intellectual, social or business life? If so, he surely must be indetifiable without too much difficulty.