Sir Paul McCartney has shunned expensive hotels in favour of camping.
The 66-year-old musician is currently on a US road trip with girlfriend Nancy Shevell, and the pair decided to spend a night under the stars when they arrived at Bennett Springs State Park in Missouri last weekend.
A fellow camper said: "It was incredible to see one of the world's richest musicians going back to basics.
"They didn't seem to have a care in the world as they laughed and joked with each other."
After spending the night in their tent, the couple further amazed onlookers when they set off on a hike in stifling heat.
A source explained to Britain's Daily Mirror newspaper: "It was nearly 30 degrees but the heat didn't slow them down at all.
"They were like two teenagers on a first date - it was really sweet.
"They were seen tucking into sandwiches. Paul even had a cheeky bottle of stout which he had packed away."