I was not aware that the Class 730s had entered service but evidently, they had three days previously with 730010 working the 06.04 Bletchley to Euston, see....
https://www.railadvent.co.uk/2023/11/new-class-730-trains-enter-service-with-london-northwestern-railway.html 730011 is seen here at Watford Junction working the 15.54 Euston to Tring London Northwestern service. The three-car sets are, of course, wearing their West Midlands trains branding and livery as these units are destined for the Birmingham suburban services due to start in early 2024 with the yet-to-enter service five-car units appearing in the more familiar green, grey and white livery.