The redheaded royal joined his girfriend at the Glastonbury festival to take in a performance by the Rolling Stones on Saturday.
"Prince Harry was great actually," festival organizer Michael Eavis told The Telegraph. "I recommended that he should go on into the night, because the nightlife is what Glastonbury is all about."
And Harry apparently heeded the suggestion.
"I told him to get his taxi driver to come back at five o'clock in the morning and do you know what? He lasted until four in the morning," Eavis added.
Harry and Cressida have been an item for about a year.
"They met through [Princess] Eugenie, who is friends with Cressida," a source told E! News last July. "Cressida is really smart, very naturally pretty and just a really cool girl to hang out. It's hard for Harry to date as there are so many opportunities out there, but Cressida is someone he knows he can trust as she is already in his circle. She's already passed the test of being discreet."
Since becoming an item, the two have been seen getting cozy after the Dark Knight Rises premiere and partying together at a club in London.
Earlier this year, Harry and Cressida displayed a bit of PDA during a ski holiday in Verbier, Switzerland. While the royal vacay also included Harry's uncle Prince Andrew and his ex, Sarah Ferguson, and cousins Beatrice and Eugenie, all eyes were clearly on the pretty pair. Most recently, the couple attended the wedding of friends Melissa Percy and Thomas van Straubenzee.
Photographers are already lining up outside the medical facilty, even though the mom-to-be isn't due for another couple of weeks.