(27 Aug 2015, 5:02 pm)Jimmi wrote Yes, Darlington trialled two Optare Solos at the same time in 2007 I think, one was allover white and was used on the 723, think at this point the 713/723 ran combined every 15 minutes between Darlington and Durham Arnison Centre, may be wrong on that. They also trialled another Solo at the same sort of time which I think they used on Darlington Town Service 21 (not to be confused with the current 21 route).
Sadly I have been unable to find any photos or information of these two Optare Solo demonstrators.
Following a quick search of Flickr I can confirm the registration of the one used on the 21 was YJ07 VRP.