My heart-stopping research saga to find out if Dorotheum’s part-painted cartoon by a "follower" was in fact a sleeper

Our pick of highlights from the next fortnight's auctions and fairs

A leading Italian art historian attributed it to Raphael and associates before the sale

The work, previously unknown to scholars, was until now in a private ducal collection

The female Italian Baroque artist's depiction of Lucretia is thought to have been in European collection since the 19th century