Robbie Williams has spoken of the "discomfort" he feels when he is approached for photos and autographs.
In a candid Instagram post, the pop star said he can "mask it well", but he feels frightened by social interaction and "panics" when a stranger approaches him.
The singer, 51, also revealed he turned down multiple requests for photos on a recent flight.
But he said he felt "gratitude" for those who tell him they are genuine fans of his, adding: "This isn't a complaint, it's context."
The former Take That singer said that during the domestic flight across the US, one fan handed him a "lovely note" and then asked for a photo.
Williams said he then wrote a note back.
"I explained I'd been up since 04:30, had two hours' sleep, and wrangled four kids through the airport. I've got bags under my eyes and I'm dealing with anxiety," he said on social media.
"I explained that if they came and took a photo with me, my anxiety would spike - because then the whole cabin would start wondering who I am."
He said another fan then asked for a photo, so he wrote a similar note on the back of his plane ticket.
"As I was writing that one, another passenger walked up and just asked outright for a photo," he said. "I obliged."
Williams said he saw it as "being of service" and that, if it made someone happy, he would do his best to facilitate.
"Still... I think there needs to be a caveat," he added.
