Hi, Maurizio. It is very difficult to photograph the whole plant because it is in a very old garden, mixed in with many other 100-year old plants. I'd call it a small tree. I can say that in my warm wine-country garden, with many summer days at 95℉/35℃, the blooms fade to white within minutes. The plant is healthy, floriferous and vigorous, but the color is obliterated in the sun.

You are right - the plant could be Lady Roberts. Unfortunately, in my climate it's almost impossible to asses the color of the blooms to compare them to the color Cant would have seen in England. I need to search for references to see which was most likely to be in commerce both in the USA and in Australia.