Max Carter, Tobias Meyer, and Alex Rotter Photographer OK McCausland The whole collection is like this, Meyer explained, never the easy works, always the tough ones, the ones Si could get passionate about before anyone. Bill Acquavella struggled for years to sell a late Lucian Freud, a nude self-portrait, a tough one. When Si saw it, he pounced, and it’s still in the collection, one of the many knockouts yet to come to market. What’s remarkable is that Si did sell so much of the collection while he was alive—he basically cleaned house in the ’90s when he moved apartments (David Geffen scooped up the big ones), simply because they couldn’t fit on the walls of the new place. He consigned to auction and to dealers, letting Larry Gagosian put stuff discreetly on the market, floating things out there. “That’s the interesting part that we haven’t talked about, Si’s editing—the ability of the pen to cross out a paragraph,” Meyer said. “He was absolutely unsentimental about selling things. I once stood in front of a …