Someone in the studio was named Herb.
I thought of that, but who at EMI was called "Herb" or "Herbert"?
I don't think the slang term "herb" was in common usage in 1966. This is from Slang-Dictionary.com:
1. marihuana, herbal cannabis. This is probably the most common name for the drug in Caribbean use (usually pronounced ’erb). The word has been given special prominence since the early 1970s by reference to it (in popular songs and elsewhere) by Jamaican Rastafarians, for whom it is sacramental. White British cannabis smokers adopted the term as an alternative to the more commonplace grass, bush, etc. in the mid-1970s.
a street urchin. A rare shortening of Herbert, typically pronounced ’erb.
a dupe. This term, heard in the 1990s in street argot, is probably taken from the proper name supposedly denoting a quintessential ‘sucker’. (H)erbert is the British equivalent.