The 24-year-old Royal and the 34-year-old singer were spotted enjoying a cosy dinner after partying the night away at a rock concert.
They dined on burgers in the VIP area of the Hard Rock Calling event held in London's Hyde Park. According to a witness, the pair exchanged warm hugs and a kiss when they met earlier in the evening during a performance by The Killers.
They watched the rockers' set together from the side of the stage.
Following the show, they retreated to the plush backstage area for a meal, joined on their secluded table by singer Tom Jones and four others.
After polishing off their food, the group ordered a round of alcoholic lemon drop shots.
"Harry looked absolutely delighted to see Natalie when she arrived," the Sun quoted the witness as saying.
"They embraced warmly and shared a quick kiss.
"They were dancing and joking together for the entire duration of The Killers' set.
"At dinner, afterwards, they carried on chatting and laughing like old friends.
"Tom Jones joined them during their meal.
"They were having a whale of a time, drinking beer and wine before a round of shots," the witness added.