(30 Mar 2017, 7:40 am)MurdnunoC wrote Didn't the X11 run between Heworth and Hartlepool only?

The X55 isn't a new idea. A similar service with the same number (operated by United) ran between Newcastle and Hartlepool (with later extensions to Metrocentre and Billingham) in the late 80s/early 90s.

I believe GNE have had 2 County Durham X11s in the last decade. First was a service between Peterlee and Heworth only, photo in link credit to Carlise Bus Group:
https://www.flickr.com/photos/stagecoachuk/14354719795/

Most recently was the Hartlepool - Newcastle X11 which has been discussed here. Photo in link credit to Tony Kuy:
https://www.flickr.com/photos/60502549@N02/6803908308/

I believe the bus in each picture was the regular on each respective service. 

The last proper fast bus between Hartlepool and Newcastle was the X99, which lasted briefly into Stagecoach days and ran from Seaton Carew. I think there was a Leyland National Hartlepool Transport has dedicated to the service as it had been rebuilt to coach spec as a demonstrator as to what their in house bodyshop could achieve, with the intention of bus refurbishment becoming a sideline. Coaches from their coach operation would be sent out too, though I'm sure I've seen images of their venerable REs making it up to Tyneside too.