Apparently LNER operated a test train today 26/6/23
https://www.realtimetrains.co.uk/service/gb-nr:K03054/2023-06-26/detailed
https://www.doncasterfreepress.co.uk/news/people/test-train-departs-doncaster-to-see-viability-of-service-betwen-cleethorpes-and-londons-kings-cross-4197335