(24 Aug 2021, 8:35 pm)Dan wrote 723 is the only Solo branded as Voyager - because it has seatbelts and a tachograph.
It's at Washington at the moment for use on the staff shuttle, but has also been used for route learning the extension of the X1 to Peterlee/Dalton Park (which I suspect is what you saw).
I see, right. Ah route learning for the X1 makes sense, never thought of that!