     let bidHistoryState = Observable<BidHistoryState>(.Closed)
     let bidHistoryDelta = Observable<(delta: CGFloat, animating: Bool)>((delta: 0, animating: false))
 
+    private var bidHistoryViewController: LiveAuctionBidHistoryViewController?
     private let biddingViewModel: LiveAuctionBiddingViewModelType
 
     private var imageBottomConstraint: NSLayoutConstraint?

            // Depending on the direction of the velocity, close or open the lot history.
            let targetState: BidHistoryState = velocity.y >= 0 ? .Closed : .Open

            // TODO: be clever about animation velocity
            UIView.animateWithDuration(ARAnimationDuration, animations: {
                self.alignMetadataToTopConstraint?.constant = self.openedMetadataPosition ?? 0 // Reset this to stick to the top, we'll set its active status below.



        // Subscribe to updates from our bidding view model, telling us what state the lot's bid status is in.
        biddingViewModel.progressSignal.subscribe { [weak currentLotView, weak lotMetadataStack, weak historyViewController] bidState in

            let hideCurrentLotCTA: Bool
            let hideBidHistory: Bool
