With the release of 2020's LEGO Harry Potter's Diagon Alley™ (75978) there has always been the gnawing thought at the back of my mind as to whether or not we'd see an extension to the set with either more shops, such as Gringott's Bank, or Borgin & Burke's—which we saw with 2011's First Rendition of Diagon Alley (10217)—or some previously unseen shops that expand the street layout further. It's interesting to note that within 75978 we may have already gotten a hint from LEGO as to a potential future expansion of the Diagon Alley™ shopping district.
Tucked in between Flourish & Blotts™ and Weasley’s Wizard Wheezes you'll find a small sign that indicates a connecting alleyway that'll lead you down to Knockturn Alley—which, according to Hagrid was a "dodgy place". It's also interesting to note that at the back of all the structures included in the Diagon Alley™ (75978), you'll find a 1x1 Technic Brick (6541), which has been cause for speculation since the set originally released back in October 2020.
With the announcement and official details of LEGO's most recent Harry Potter Minifigure Set— Wizarding World Minifigure Accessory Set (40500)—it seems there may be a further hint at a potential, darker expansion to the famous shopping district. Included in the set are another Harry Potter, Mr. Borgin and 2 generic wizard minifigures.
Why would they be including a Mr. Borgin minifigure in the set, if the last time we saw a Borgin & Burke's shop was in 2011 with the first Diagon Alley set? It's possible this may be an allusion to an eventual expansion of the shopping district. I don't expect we'll see the current Diagon Alley™ (75978) disappearing from shelves anytime soon, having just released 7 months ago, but it's definitely cause for speculation. There's no official information that suggests we'll be getting a Knockturn Alley set, but it would certainly make for an excellent expansion, and would help to explain why there are so many Technic Pin connection points on the current Diagon Alley™ (75978) set!
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