Their progress was one of a procession, so the accident was witnessed by several drivers, along with some of the guard and a the youngest prince.
Stephen had changed his clothes into those of a guard and had joined the ranks to line the path from the palace to the kingdom. His mother knew nothing of this, though Stephen had been doing so for well over 2 years now. It was how he'd met Hiro and the only ones who knew were Hiro and the General, Kelin. His father understood that he went to the imperial training grounds to learn with the other soldiers, but not that his own son had been an active part of the guard. Of course, the other soldiers didn't know who he was. No one paid Prince Stephen much attention, so why would they realize that the kid named Wren was in fact royalty.
It had been Kelin's idea, which had been discussed with the king. They'd offered Stephen an opportunity to be active and, though they didn't say this to him, prevent him some becoming too insular. Kelin would keep a close eye on him and no one was to know who he was.
Unfortunately, Hiro was brighter than most and keen, so when he realized he was sworn to secrecy.
The accident had happened a little beyond the gates, caused the scream of horses, shouts and cries. Stephen, along with several other guards, ran to the rescue of the carriage. They were all fully helmeted, their faces masked completely, and identical in their uniforms, but they worked like one, two going to the rescue of the driver and the other 5 to that of the occupants. 
Stephen and 2 others were hoisted onto the side of the carriage to help those inside, the other 2 awaiting report.
Stephen opened the door within to see how the occupants faired, saying that he would climb inside and pass them to the others. 
His heart almost stopped when he realized whose carriage he was now looking into and how was within.
"Send word to the palace," he shouted. "It's Baron Kent and Lady Alessandra."
A ripple went through those around and Stephen could imagine the message being passed. It was not a secret that Lady Alessandra was practically a royal child herself and a great favourite of the Queen.
Stephen turned back, to decide what was the best course of action.

ooc: I've not put any detail as to how the occupants are etc. I thought I'd leave that bit to you. ;)