Over 10% of "gold standard" forgeries of 20th century paintings went through Christie's

More than 30 paintings collectively worth an estimated £30 million were recently found to be forgeries of major 20th century artworks. Unsurprisingly, the forger's strategy is believed to have been "to create compositions that would relate to titles of documented works whose whereabouts are not currently known." Experts described the forgeries as "gold standard" but some of the works' inauthenticity possibly could and should have been discovered by the leading dealers and auction houses that sold them -- especially since a painting's provenance or history can apparently be discerned from labels or drawings on the back of it. For example, one of the four forgeries auctioned by Christie's had a fake label for "Flechtheim Collection" and it was this very label that aroused suspicions. I don't doubt how seriously the major auctions houses take issues of authenticity and provenance but it seems to me that failing to detect a fake label is hard to excuse and not comparable to not undertaking the (hugely expensive) expert scientific analysis prior to auctioning a painting (plus, I can imagine that having an expert do so is a double-edged sword because you can inadvertently taint a work that was authentic to begin with).