Does a viral image show the national flag of the United Kingdom, also known as the Union Jack, "flying at half-mast at some Government Buildings" in the UK in March 2024? No, that's not true: The photo was taken in 2022. It captured the lowered flag after the death of Queen Elizabeth II.
The claim appeared in a post (archived here) published on X, formerly known as Twitter, on March 17, 2024. It opened:
BREAKING: Reports that the Union Flag is flying at half-mast at some Government Buildings across the United Kingdom tonight amid reports the BBC is on standby for an "imminent announcement" from the Royal Family. #RoyalFamily #BBCNews #KingCharles #KateMiddleton #PrinceWilliam
This is what the post looked like on X at the time of writing:
(Source: X screenshot taken on Mon Mar 18 16:34:13 2024 UTC)
The image went viral amid a wave of online rumors about King Charles' health (archived here) on Saint Patrick's Day.
One of the accounts (archived here) that pushed the claim on X used the handle: "BBC ROYAL FAMILY ANNOUNCEMENT π." The account has no official tie to the BBC or the royal family.
What its post presented as a sign of the purported soon-to-be-made "imminent announcement" was an old photo.
A reverse image search shows that the image was initially published (archived here) in 2022 by the Anadolu Agency, a Turkish state-run news agency. It illustrated a story about Queen Elizabeth's death. Contrary to the claim, the photo wasn't even taken in the UK: 
(Source: Anadolu Agency screenshot taken on Mon Mar 18 14:56:19 2024 UTC; the content of the page was automatically translated to English by Chrome)
As seen in images of the British Consulate General in Istanbul published on Google Maps (archived here), the building's roof has a distinctive edge that matches the one seen in the photo in question.
No English-language news outlets (archived here) reported that the national flag flown at this location was lowered in March 2024.
Other Lead Stories fact checks discussing international topics can be found here.
