It was a bolt from the red, white and blue. A few weeks ago the youngest daughter of Thailand’s ageing king posted several photographs of herself on social media. One of them showed her with hair braids of red, blue and white; another of her wearing a similarly-striped bracelet. These are the colours of Thailand’s national flag, but they have also come to be associated with the anti-government protesters who have rocked the country as they seek to oust Prime Minister Yingluck Shinawatra.
Whether or not it was her intention to do so, the posting of the images by Princess Chulabhorn Mahidol was widely interpreted as a sign of her support for the anti-government forces.
"It was seen as a declaration of war," said a Thai political analyst sympathetic to the government, who asked not to be named. "Her doing that gave a symbol that elements within the palace support this protest 100 per cent."
The furore has drawn attention to an issue that is rarely discussed in public, but which some say is crucial to understanding what is happening in Thailand.
While the conflict is fuelled by several factors, say those analysts, the declining health of 86-year-old King Bhumibol Adulyadej and the behind-the-scenes jostling for position ahead of his succession is a major driver of the turmoil playing out on the streets of Bangkok.
Some consider it nothing less than the fall-out of a dynastic battle in which the children of the king have taken different sides.
"The old elites have never cared about democracy. But when the king dies they want to be sure that they control the parliament," said Andrew MacGregor Marshall, a journalist and author of an upcoming book on Thailand titled A Kingdom in Crisis.
According to the rules of succession, on the death of the king the throne should pass to Crown Prince Maha Vajiralongkorn. But within the palace establishment - the network of privy counsellors, advisors and minor royals - are those who would prefer it instead went to Crown Princess Maha Chakri Sirindhorn. Princess Chulabhorn, who posted the images on Instagram, is said to be an ally of the Crown Princess.
One reason for the opposition to the thrice-married Crown Prince is his reputation as a playboy.
In 2009 a video emerged that was apparently taken at a birthday party for his poodle, Foo Foo, and which appeared to show his wife, Princess Srirasmi, wearing nothing but a G-string.
Others apparently simply believe the Crown Princess would be easier to control than the Crown Prince, who is considered a maverick and who may sweep away many of his father's courtiers.
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.
In a 2009 briefing for then-US Secretary of State Hillary Clinton, which was later published by Wikileaks, the US ambassador Eric John said: "It is hard to overestimate the political impact of the uncertainty surrounding the inevitable succession crisis which will be touched off once King Bhumibol passes."
The battle is not being fought for small change. Forbes magazine has estimated that King Bhumibol oversees assets worth more than £18.2bn. Whoever succeeds him will control a huge network of patronage and influence.
While the tug-of-war over the succession is of crucial significance, the topic is almost never discussed in public. Thailand's tough censorship laws that prohibit criticism of the monarchy and carry a penalty of up to 15 years, are often used to silence critics.
As a result, discussion of the royal succession issue is confined largely to private conversations or anonymous comments made online. As such, those who study Thailand’s monarchy are required to watch for small but significant signals, in much the way that students of the Kremlin once studied the relative position of leaders on official photographs.
Those who seized on the posting of photographs by Princess Chulabhorn, point out this is not the first time she appeared to show support for those opposed to Mr Thaksin. In late 2008, she and her mother, Queen Sirikit, controversially attended the funeral of an anti-government protester. In 2011, she told a TV chat show that supporters of Mr Thaksin were responsible for the declining health of her father, the king.
"Given the massive stakes involved in the succession, it would not be surprising if there are other contenders," said Professor Patrick Jory, of the University of Queensland. "I don’t think it was accidental [that Princess Chulabhorn posted the images]. She wanted to show she is on the side of the protesters."
Efforts to contact Princess Chulabhorn failed. The listed phone numbers of her office do not work and she did not reply to a question on social media.
Another blue-blood who has made public her views is Malinee Chakrabandhu, a descendant of King Rama IV, who ruled Siam in the 19th century. She posted a photograph of herself wearing a T-shirt that read: "I support the Crown Prince."
In an interview at her tastefully-decorated home where photographs of her with other royals - including Britain’s Prince Charles - adorn the walls, Ms Chakrabandhu denied being a "signed-up" supporter of the government.
But she said she opposed the anti-government protesters and had fallen out with several family members over the issue, including her daughter.
"I back the Crown Prince. Nobody else. He is next in line and we have no right to change that."
The 66-year-old Ms Malinee, who uses the title Mom Rajawongse, or MR, a signifier of her royal heritage, said: "Most Reds also support the Crown Prince. But most MRs are yellow [anti-government] and that disappoints me very much."
The current stand-off in Thailand is not only about the succession issue. Among the protesters who have seized control of parts of Bangkok are farmers, particularly from the south, and middle-class citizens who believe Mr Thaksin oversaw widespread corruption. They are angry over an amnesty bill that would have allowed him to return to Thailand.
The leadership of the protesters has claimed there is no-one pushing them to act or funding them. "We are not claiming we have the support of the royals. This has nothing to do with the monarchy," said Akanat Promphan, a spokesman for the protesters.
But others on either side of the dispute believe members of the royal family have shown their hand, something that was inconceivable in Thailand just a few years ago.
Supon Fumuljaroen, a senior leader of the Red Shirt movement that largely supports Mr Thaksin and his sister, said he believed the protests involved several issues.
"The king is very old now," he said. "The privy counsellors, the elite, the aristocracy: they are all used to the benefits of His Majesty's power and they feel the person they want to succeed may not."
And many of those gathered on the streets in Bangkok - driven to protest by whatever reason - also saw the posting of the Princess’ photographs as her signalling her support to their attempt to oust the government.
One protester, Kanda Ruengmaswan - a woman who was last week part of the protest at the capital's Pathumwan intersection - said: "The princess cannot give a speech but she wrote that to send a symbol."