In The Best Offer, why does Robert (Sturgess) manoeuvre Oldman (Rush) to take him along when he has dinner with Claire? How does this help his scheme?
I think that's also a part of their (Robert and Claire) plan. After Robert seeing Claire, he tells to Virgil something like "Claire is more beautiful than you described and I think I like her" and Virgil replies "are you trying to make me jealous?"
Since Virgil firmly believed that Robert is expert on women's matters, I think Robert is trying to send a subliminal message to Virgil Oldman that Claire is beautiful, this will result in having Virgil to be more addictive of Claire.