Reeva decided he would keep the fact under wraps for now. Revealing that he was an apostle could trigger reactions from priests who weren't devout enough. Imagine discovering that the criminal you're escorting turns out to be Jesus himself—it wouldn't end well. He'd likely meet the same fate as Jesus at that rate. You never know how someone with shaky beliefs might respond to an apostle, especially when that apostle also happens to be a branded heretic.
Still, Reeva could tell a few key people. Those higher up might react differently than the average priest. One such person was the blue-haired royal guard who came to escort the prince. She seemed like someone who would protect him if things took a turn for the worse. Despite the priests' dislike for the royal guards, they weren't true enemies.