The Orient Express (Venice Simplon-Orient Express) can "start" in London, but the restored antique train has never run in the channel tunnel. I've seen it done

The Orient Express (Venice Simplon-Orient Express) can "start" in London, but the restored antique train has never run in the channel tunnel. I've seen it done differently in most of the YouTube-hosted videos I've seen. The current method uses Eurostar to get to France and transfer to the antique train. Previous methods involved transfers on the British side from a fancy "Pullman" train.