(26 May 2015, 3:55 pm)Dan wrote citaro5284 explained this previously to tyresmoke - it relates to the re-fuelling system in place at Riverside.
Note the little black thing on the 'h' in the photo below:
Go North East: 4941 / NK51OLC by Daniel Graham, on Flickr
This is just hidden away from the public eye on 5391 - 5394, as all the various holes in the bodywork don't look particularly attractive, as per the Scania L94 above.
Ah soz. Im not usually one for missing posts. Cant say the highwayman livery makes the solars look good anyway so it doesnt make too much of a difference.