That was probably slightly later, as Dan Air were still doing the Newcastle at the time when the East Coast routings first started.
When Air UK started EDI/GLA - STN, they seemed to favour this route, too. I once heard a Pennine Radar controller down-grade the service to flight information "due to density of traffic" to one southbound Edinburgh when approaching The Vale of York. This woke the crew up somewhat. I didn't think that this was allowed...