Hohenlohe

Her son, Hubertus von Hohenlohe, said she died after breaking her ribs and perforating her lungs in a domestic accident.

“I was surprised. It was a fantastic painting. Find me another,” said Heinrich zu Hohenlohe, a Berlin-based art adviser and dealer, who was mystified by the lack of competition for such a historically important work.

“It was a high starting price, but it was the right price,” zu Hohenlohe said.

Heinrich zu Hohenlohe, an art adviser based in Berlin, said Sotheby’s had “struggled to get works for the post-Brexit sale.”

It is thought relatives of the two German princesses - Sophie von Hohenlohe and Charlotte Federica of Mecklenburg, who died in the 19th Century - had been invited to attend but it was unclear whether they would do so.