Sting performed at Glasshouses in Chelsea to support a close pal, photographer and philanthropist Bobby Sager, at a party for Sager’s new book, “Invisible Sun.”

Sting sang his famed Police tune “Invisible Sun,” and joked that Sager must’ve ripped off the name.

The book features powerful pics Sager shot of kids in Syria, Rwanda, Afghanistan and other countries over two decades. The images will be featured in a show at soon-to-open Fotografiska New York this winter.

Also spotted: Trudie Styler, Chris Botti, Carole Radziwill, Heather Thomson, Danny Clinch and Mike Novogratz.