Sienna Miller has spent £5000 on a gift for Factory Girl co-star Hayden Christensen.

The actress bidded for an original Andy Warhol screenprint of Hayden's idol Grace Kelly, before delivering it personally to his trailer.

"Hayden was so touched," an insider told the Daily Star. "He has always dreamed of owning his own Warhol."

The pair are rumoured to be "more than just good friends".