There might have been a considerable lack of disrespectful fanfare when United States president Donald Trump was in Singapore last month, but Londoners, as it would appear, have a particularly in-your-face way of expressing themselves.
Its advice to USA citizens was to "keep a low profile" and "exercise caution if unexpectedly in the vicinity of large gatherings that may become violent".
The briefing also urges Americans to "be aware of your surroundings" and 'monitor social media for updates'.
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The watchdog also announced plans to a bring a criminal action against Cambridge Analytica's defunct parent company SCL Elections. It's not the first time, however, that Europe has penalized Facebook.
The "demonstration alert" issued by the embassy also tells Americans to "exercise caution if unexpectedly in the vicinity of large gatherings that may become violent".
With tens of thousands of Brits signed up to take part in the protests of President Trump's policies, the embassy further warned that "several of the events are expected to attract large crowds and there will be road closures in connection with these events". "We don't know when. But let's be ready - and be prepared to take to the streets in the most incredible protest in our history".
Demos on Thursday include one near Blenheim Palace in Oxfordshire where Mr Trump will attend a black-tie dinner, and another not far from the USA ambassador's residence in Regent's Park, where Trump and his wife Melania will stay overnight. The news outlet notes that a counter-protest to welcome the president is scheduled for that day as well.