The Lydian Baker — David Wishart

When the solid gold statue of a female baker gifted to the oracle at Delphi by King Croesus of Lydia and missing for over three centuries unexpectedly reappears on the Athenian black market, Corvinus's stepfather Helvius Priscus recruits him as go-between in the purchase. Priscus, though, it turns out, isn't the only interested party, and where bidding methods are concerned his rivals don't play games... The fourth book in the Marcus Corvinus series.