Second post in an hour - God, I’m on fire today!
After scouring the ‘net for information on what’s just happened to me, I came across some forum posts and explanations for a process called ‘deloading.’
Basically, what happens is if you hit a plateau, you reduce (deload) the amount of weight you are using, and sort of build back up, and is described as an effective way for breaking through plateau’s.
In all honesty, I don’t think what I experienced today was a plateau - more of a bad day - but it’s worth baring in mind, just in case.