The important thing is to phone. They might give you a lot of static or might say OK and make a note on the record.
If you don't phone and don't fly the first segment, the rest of your itinerary will be cancelled.
I have done this in the past but only once or twice a long time ago and they OK'd it. I just explained that it was impossible to get to the origin airport on time but I could get to the next one.
[This message has been edited by BlondeBomber (edited 09-09-2002).]