A £750,000 Andy Warhol painting, stolen in July, has been recovered in mint condition with the help of the Art Loss Register (ALR).
Munich art dealer Bernd Klüser had sold Warhol's Portrait of Lenin to a private collector in June.
The 1987 acrylic on canvas of the Russian revolutionary's head was stored in a warehouse in Cologne on its way to its new owner when it was stolen.
It was registered with the ALR within 24 hours of the theft, rendering it virtually impossible to sell in the international art market.
Klüser was then contacted by an anonymous source who offered to return the painting for an undisclosed reward put up by the painting's insurer Mund & Fester.
The painting was returned, identified as authentic and is now awaiting forensic testing by police.
Aon Artscope director Klaus Behrens praised the ALR's work on behalf of the insurer. He said registering the painting on the ALR had prompted the thieves to return it.
ALR German managing director Ulli Seegers said: "We're delighted this art mystery has ended so satisfactorily for all concerned."