Then came the grand finale, and a moment that would take us from habanero to Carolina Reaper on the Scoville Scale. Enter John Mayer and Slash for an all-star set-closing performance of La Grange.

While on record ZZ Top are often explorative, and sometimes downright weird, in concert the surprises are few and far between – even down to their chest-length beards, dusty hats and cheap sunglasses.