Really? This is the only movement that wasn't a service train. Seems more likely it was a 387 of some sort (and confirmed as 387202 elsewhere).The future for Thameslink is evidently the past - a Northern 319 was seen in the core on Saturday afternoon!
Realtime Trains | 5O87 1526 Hornsey E.M.U.D. to Lovers Walk T&R.S.M.D | 06/08/2022
Real-time train running information for 5O87 1526 departure from Hornsey E.M.U.D. to Lovers Walk T&R.S.M.D on 06/08/2022. From Realtime Trains, an independent source of train running info for Great Britain.
www.realtimetrains.co.uk