Aug 2019 it was announced we'd signed a new 12 year deal worth £100million with Amex for them to sponsor the shirts, ground and training ground. From reading Barber's notes, although the wording isn't clear, I think this is what he is referring to rather than a new deal. I'm fairly certain a new deal over an above the 2019 one would get more than 3 or 4 words towards the end of some notes about the season in a match day program.
I may be wrong but as far as I remember it was agreed and announced in 2019 but only comes into force next season. It is a remarkable deal and will change our income from Amex by 20 fold on the original agreement a decade ago.