Before the era of the paparazzi, Hollywood stars would pose for glamorous portraits for their adoring public.

Today an astonishing collection of never before seen photographs, featuring iconic figures from the Twenties to the Forties, go on show in London.

Images of stars like Elizabeth Taylor, Marilyn Monroe and Clark Gable form part of a new exhibition called Glamour of the Gods: Hollywood Portraits, which opens at the National Portrait Gallery.

Organised by the Santa Barbara Museum of Art, the photographs come from the archive of the London-based John Kobal Foundation.

Images like these were instrumental in transforming actors into international stars. They were used as posters and postcards and still attract hordes of admirers.

This new collection of 70 photographs and prints will be shown alongside vintage film stills from classic movies including Lillian Gish in The Wind, Fred Astaire and Ginger Rogers in Swing Time and James Dean in Rebel Without  A Cause.

John Kobal was an avid film historian and collector of Hollywood film photography. He donated his entire collection of negatives and fine art photographs to his foundation prior to his death in 1991.

He began collecting film photographs in the 1950s, visiting Los Angeles frequently where his interest began to shift to the photographers behind the portraits.

Film and art critic John Russell Taylor, who has written an overview of the project, said: 'Of John it can be said with certainty that he did something no one else had thought at that time to do.

'When he became interested in the men behind the images, almost all of them were still alive and reachable.