According to TRUST, Grand Central will achieve the extension of their fifth train which currently runs as 12.53 Kings Cross to Hartlepool and 14.47 Hartlepool to Kings Cross to run to and from Sunderland. The southbound train will depart from Sunderland at 14.06 and have a 17 minute dwell at Hartlepool to pick up it's current path. It still won't call at Thirsk.
I'm curious to see how that will work. The current 14.47 Hartlepool to Kings Cross is the return leg of the 11.21 Kings Cross to Hartlepool (Arrive 14.23).
In order to get to Sunderland to return at 14.06 its going to have to leave kings Cross an hour or more earlier. Based on current times the northbound train is going to have to leave around 10.00. I think it's going to involve a lot of re-organisation to make it work.