Ask almost anyone who books speakers for a living and they'll tell you the same thing, usually with a slightly rueful look: the talk that gets the biggest reaction on the day isn't always the one that changes anything.

A lot of event organisers have sat through versions of this. The polished speaker, the well-rehearsed story arc, the room buzzing on the way out – and then nothing. No one doing anything differently a month later. No shared language, no shifted habits, no detectable change in how the team works. The energy evaporated somewhere between the venue and the car park.

The real test of a keynote is not the applause. It's whether anyone is doing anything differently weeks later. That's the measure that matters, and it's also the one that's hardest to buy for in advance. You can watch a showreel. You can read testimonials. You can't audition behaviour change. So you end up optimising for the wrong signal, and sometimes getting a very expensive room full of people who feel inspired for an afternoon and then go back to exactly how things were. Here's what to look for instead.