(24 Jan 2016, 4:55 pm)South Tyne Lad wrote 156s are diagrammed to work most Newcastle - Carlisle with few interworking at Carlisle to work the Heaton diagrams on the Cumbrian Coast aswell as the daily 1622? Newcastle to Whitehaven,
Only time a 156 could appear is on the early morning Saltburn to Newcastle via ECML peak working which then again, Works onto a Carlisle service. Though I believe this is a 142 Diagram.

But because of the Landslide around Corbridge, Heatons allocation has gone through the window with 156s stuck west of Hexham and 156s stuck east of Hexham.
So Heaton send them out to Strengthen other services instead of 142s, Until the landslip is cleared at Corbridge all of Heatons diagrams will be worked by either 142s or 156s with no confirmed type to run the service

The 158 will be coming to use Heatons wheel Lathe.

I get what you're saying about the blockage on the Tyne Valley line but there were increasing sightings before it happened. Some mentioned in this thread.

Initially the sightings seemed to coincide with closures down in the Boro area.
There haven't been any closures in that area for a while though.