A Second Copy of Music Cipher to Charles II Acquired by the British Library (ca.2018)

Sheet music concealed a secret message to Prince Charles (later Charles II) fleeing after the defeat in the Battle of Worcester: "Conceal yourself. Your foes look for you." Another version concealing the same message is said to be for another Prince Charles, Jacobites' Charles III known as the Young Pretender. Both of these have a plausibly sounding story of their provenance. I wrote about these in "Musical Notes Concealing A Warning to Fleeing Prince Charles" back in 2015.
What I didn't know then is that the cipher to Charles II quoted in my article is in the British Library (Add MS 45850, f.68), but its provenance through the Port family I found in googling is about another copy, which the British Library newly acquired (as of February 2018) (Add MS 89288). I learned of this in the British Library's blog article, "'Conceal yourself, your foes look for you': revealing a secret message in a piece of music" (20 February 2018).

I was reminded of this topic when reading Nadine Akkerman and Pete Langman (2024), Spycraft, which refers to Nadine Akkerman (2018), Invisible Agents (the BL's blog also mentions forthcoming publication of this book). Akkerman discusses the nineteenth century copy in BL Add MS 45850 and considers it a hoax. Her dismissal of Jane Lane as the author based on the latter's literacy level is convincing. Even if we assume other authorship, it is hard to think of circumstances in which this kind of cipher came into play ("it is not as if Charles Stuart did not know his enemies were searching for him" etc.).