The experienced reporter was handcuffed, shackled and placed in a red prison uniform while being detained for more than six hours in a police cell, in an incident which was described as “very concerning” by the Foreign Office.
He now faces a charge of “failure to disperse” carrying a maximum penalty of 364 days in jail and a $5,000 (?4,000) fine, despite having been alone at the time of his arrest, having remained on the right side of police cordon tape and having shown his press credentials when challenged by officers.
The Society of Editors has called for the prime minister to raise concerns over the treatment of journalists by American police following a series of arrests, particularly during the Black Lives Matter protests.
“This is no longer the US I’ve loved since my first visit in 1963,” said Mr Simpson.
And the BBC’s North America editor Jon Sopel said the incident was “hair-raising, disturbing and depressing”.
“In the abstract I can’t quite believe this is happening here, in the country that’s been my home these past six years,” said Mr Sopel. “But in reality, of course, I can.”
Ian Murray, executive director of the Society of Editors (SoE), called on Mr Johnson to raise the issues of press freedom and the safety of journalists directly with President Trump.
He said that the Seattle case followed the arrest of UK national photojournalist Adam Gray, who was thrown to the ground by police, restrained and handcuffed as he chronicled protests in New York City earlier this year.
“The SoE is adamant that words are not enough. It is all well for the government to speak fine words about press freedom and the safety of journalists, but actions speak louder than words,” Mr Murray said.
“Journalists need protection to carry out their vital work to defend democracy wherever they may be working. In the case of Andrew Buncombe, it is essential that the UK government makes plain that when a journalist is carrying out their profession within law that they are provided with the protection that any liberal democracy demands. To do else is to betray the communities and society that they serve.”
Christian Broughton, editor of The Independent, said: “It is imperative that democratic leaders everywhere stand up unequivocally for truly independent journalism. The arrest and appalling treatment of Andrew Buncombe must be condemned.
“As a global news organisation, The Independent has correspondents based permanently in countries with poor records for press freedom, and we frequently send reporters into conflict zones and dangerous situations. So when the phone rings to tell you a journalist has been arrested, you don’t imagine that the correspondent in question would be in the United States.
“Andy is an experienced and highly respected reporter. As he writes in his article, the job of a journalist is not to disperse. Our job is to be present.”
A Downing Street spokesperson made no comment on Mr Buncombe’s specific case, but told reporters: “The prime minister has been clear on many occasions that he believes in the freedom of the press.”
UK consular staff gave assistance to Mr Buncombe on the day of his arrest, and it is understood that diplomats at Britain’s embassy in Washington have raised the issue of UK journalists being subjected to police action with the US administration.
A Foreign Office spokesperson said: “We provided consular assistance to a British man after he was taken into custody in Seattle and were in contact with local authorities.
“This arrest was very concerning. Journalists all around the world must be free to do their jobs and to hold authorities to account without fear of arrest or violence.”
The deputy director of research for Amnesty International USA, Justin Mazzola, said that Buncombe was one of at least 60 journalists arrested as they covered Black Lives Matter demonstrations in protest at the police killing of George Floyd this year.
“The media has an important role to play in protecting the right to freedom of peaceful assembly, but especially right now, when society is taking to the streets to protest the unlawful killings of black people by police while simultaneously combating a highly contagious virus,” said Mr Mazzola.
“The media have a right to attend and report on these protests, and law enforcement officials have a responsibility not to prevent or obstruct their work. If not, human rights violations like the ones we have witnessed over the past two months will breed in the darkness.”
Former Labour MP Ruth Smeeth, now chief executive of Index on Censorship, said: “Journalism matters. Our free press matters. This is an absolute disgrace. We stand with Andrew Buncombe.”
And the president of the Association of Foreign Correspondents in the United States, Thanos Dimadis, voiced his organisation’s solidarity with Buncombe, who he described as the victim of “unjust and blind police violence”
“Violence and intimidation against journalists here in the US have their roots in the denigration of the media by President Trump, who has adopted such a tactic as an electoral and political policy,” said Mr Dimadis.
“When media and journalists are verbally threatened with intimidation and bullying by the leader of a country, the end result is violence and intimidation of journalists attempting to challenge that leader’s decisions on the streets.”
Veteran newspaper columnist Peter Oborne said: “A proper British foreign secretary would complain forcefully about this. But I expect Dominic Raab will kowtow to the US, as he did over the killing of Harry Dunn last August.”
Labour’s shadow culture secretary Jo Stevens said that the correspondent’s experience at the hands of US police meant it was time for ministers to show that the government’s professions of support for a free press are “more than words”.
“The shocking arrest of Andrew Buncombe in the course of his job is part of a worrying increase in the clampdown of journalists in Trump’s America,” said Ms Stevens. “Freedom of the press is an essential test of a properly functioning democracy.
“Last year the Foreign and Commonwealth Office campaign for media freedom drew criticism for lacking focus and resources concentrating instead on a high-profile conference in London. The case of Mr Buncombe is the chance for the government to show that protecting media freedom and the rights of British journalists abroad involves more than words.”