From photos on Flickr, I think it is YJ19HVC, which was numbered OME2652 whilst operating for Metroline, then spent some time at Go North East, before going to COP26. OME2652 is in the middle of a batch of buses Metroline uses on route 134, so I asume it was owned by Metroline, otherwise it would have been tacked onto the existing batch. Either Metroline has loaned it back to Optare/Switch for demonstration purposes, or Optare/Switch have bought it back. Hence my earlier question about why Metroline no longer need it.