As other organisers will know, arranging a successful event takes a great deal of planning.
Speakers are invited months ahead and are contacted again before the event; therefore there is no excuse for non-attendance unless some unforeseen disaster occurs, in which case they should inform the organiser as soon as possible.
Flyers advertising the events are produced and widely distributed, and the radio and press are contacted. A great deal of publicity takes place
The two names mentioned above have in the past also let down other organisers.
Neither of them even wrote to apologise.
There is nothing worse for an organiser than having a speaker who does not appear. The crowd becomes increasingly restless and then finally the organiser has to improvise.
A really terrible situation and enough to give one nightmares for some time afterwards.