I'm going into Manchester tomorrow, a week after having seen my first GA 720s in the flesh last Friday around Ilford and Stratford. However, I can't answer as to what it's doing up here.
mod note - for speculation as to whether Northern could do with a fleet of Class 720s see:
Maybe Northern will procure a fleet of them and they're using it to test the lie of the land. 5-car would be good for many services here, with an occasional 10 in the peaks midweek even if some coaches in the rear unit are locked out of use due to platform lengths.
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