The prince is also seen to be close to ousted prime minister Thaksin Shinawatra, who is the brother of the current premier and remains a pervasive force in Thai politics from his home in Dubai.
Mr Marshall said if supporters of the Crown Princess can oust the government of Ms Yingluck and appoint another prime minister, they could control the parliament, which needs to approve the royal succession. "It would have to be done quickly," he said.
The controversy over the succession of King Bhumibol and the anxiety of those surrounding him who fear losing position and privilege, is nothing new.