Communicate ASAP. If a significant change comes up – for instance, you want the speaker to shift focus to a different topic, or the schedule has been rearranged – inform your speaker immediately. Most professional speakers will do their best to accommodate reasonable changes, especially if a big news event or organisational shift occurs. However, last-minute changes can compromise quality; major pivots a day or two out might not be feasible. If you suspect a change might be needed (even a few weeks ahead), flag it as early as you can. And be prepared: substantial content changes very close to the event could incur additional costs or not be possible at all.