For the pilot program, ACTs were procured in two consignments, which provided an opportunity to track the first consignment's sales before procuring the second consignment.
The lack of consignments by the executors of estates forced the auction houses to rely on voluntary consignments, which are difficult to secure in an uncertain market.
They import ecstasy as part of mixed consignments which Customs and Excise calls "cocktail loads".
Being able to offer guarantees as inducements to sell was an important element in securing the first consignments, which inspired other collectors to offer marquee works for auction.
They had become so lazy, so fat on the proceeds of the last two consignments which had come down from Andorra in the night, that they cleaned nothing and threw nothing out.
A spokesman for Christie's, Toby Usnik, said: "We take such allegations very seriously and will be reviewing any consignments which give us cause for concern and taking such steps as we consider appropriate".
The consignment, which includes works by Henri de Toulouse Lautrec, Paul Gauguin, Pierre Bonnard and Pierre-Auguste Renoir, is led by a painting by Claude Monet.
The family divested itself of some furnishings, including the de Kooning, which is on consignment at Gagosian.
The bulk of the consignment, which has a very short shelf life, was sent on by air for sale in the US.
Some companies, however, try to avoid prior notification of consignment, which is voluntary for plant products.
