With both of them knowing their destination (hopefully Peridot isn't bouncing Childermass too much, or Lambert will stop her and take him from her before then) they make quick enough time, and he'll carefully lift the magician in his arms once they get there.

"Can you get the door?" He nods. "Should be open. Don't exactly keep it locked."

He assumes she'll turn back, since being a dragon in a trailer doesn't seem like a good time.