It was. Peter Green, my favourite guitarist, was not in Chicken Shack, their guitarist was the very good Stan Webb.
The original female vocalist for Chicken Shack, Christine Perfect who later married John McVie played piano and did back up vocals on some Peter Green Fleetwood Mac tracks before later joining them after he had left.
Although I am a big fan of Etta James I prefer the Chicken Shack version, one of the best British blues records.
I'm glad it isn't just me who prefers the Chicken Shack version. I remember having to find a compilation with it on. The pre-internet days could be frustrating at times but some much more enjoyable trying to find what you want in a record shop.