Mike4 wrote:So my question is, does flour genuinely degrade in storage or are the manufacturers just pandering to consumer expectation (or possibly regulations) that a 'best before' date is marked on the packs?
Will I kill myself if I make bread from the June 2021-expiring flour?
You won't kill yourself, it'll be fine, but flour does stale eventually if you leave it maybe 5 years, it just doesn't taste very nice. If it smells OK, you'll be fine.
Ergot doesn't grow in flour, it's a disease of living plants (mostly rye) but it's evolved to make fruiting bodies that are just the same size as cereal grains so historically they would slip through the threshing process with the grain. There's very strict limits on it in modern agriculture though, so don't worry about it being in your daily Hovis.