Mycroft and Harry Potter ARE the British government

[sheffsfic.livejournal.com]

Hello kindly finders: does anyone remember a BBC Sherlock crossover with Harry Potter, where not only is Mycroft the British Government (muggle) but also Harry Potter is the British Government (magic) - in other words they're both a kind of symbol or personnification of the nation.  They're not IN power, they ARE power.  It was a neat concept and I'd very much like to revisit it.  Possibly a series, possibly on AO3?  Thanks for any help you can give.