170519 is the unit the signal is off for and it forms 1M08 0728 Cambridge to Liverpool Lime Street.
Turbostar 170507 runs east for Norwich with 1L15 0952 from Liverpool Lime Street.
Framed by the down advanced starter is Trans Pennine 158761 on a diagram that includes 1B73 0927 Cleethorpes to Manchester Piccadilly.