I wrote:
The John Innes formulations for seed and potting composts have long
been in the public domain.

Hmmm, maybe not !

(mine is in a a book, but give me a mo. I'll find it on the web
somewhere I'm sure !! )

a brief google, I was sure, would lead me to the John Innes Institute
where all would be revealed ! Sadly no
So perhaps I've been under a delusion these past few decades

If you need to follow the DIY route then we could exchange emails and
I'll send you the info that I have in my library !