It's not a first for Cunard either. It happened with QE2 in Southampton in the 90s. I'll need to do some digging for the details. Either a repair, or refit, wasn't completed in time (surprise, surprise) and rather than delay the next cruise (or crossing) the passengers boarded while the ship was still in drydock. She was re-floated and, with only one engine running for the hotel load, she was towed down Southampton Water as the Engineering dept. scrambled to get more engines up and running. Able to come under her own power only after they passed the Nab Tower.