Anyone understand book reference notes

[Mitch in Notts]

One of my lot appear in a court case in Gentlemen & Poachers by PB Munsche published in 1981. But I`m having problems with the reference notes. The exact entry is:

B.L., Add. MS 42599, p. 46v; Norfolk R.O., How 750/75. See also ibid., How 750/63.

I guess MS might stand for Manuscript, but what is B.L. and is How a name or what? I know that the reference is to Norfolk Record Office|oopsredfa But I was expecting something simple like `See Norwich Mercury of 21 Jun 1066` but at present I don`t even know the date of the court case for poaching!

Many thanks

Mitch

[Jan1954]

Immediate thoughts.....

B.L. = British Library
Add M.S. = additional manuscript
p. 46v = page 46v (?)
See also ibid = abbreviation for ibidem (Latin ‘in the same place’), reference to a book, chapter, or page previously cited as in How 750/75 and now How 750/63

Unable to help with How, though.....

Is this of any use?

[Mitch in Notts]

You lot never cease to astound me with your sheer brilliance.
And we have a connection to Castle Rising as well!
So when I go for my annual visit to Norfolk Record Office, in 11 months time :(, I`ll do a thorough investigation and hopefully get a date for the event.

Thanks again

Mitch

[Mitch in Notts]

I did thanks Finbar, though I`d zoomed in their as soon as I saw the Howard Collection notes!
I`ve found HOW 750 which puts the event between 1798-1817. I feel 1816 is likely. Brilliant thanks