Class 60.

60005 'Skiddaw' in Railfreight (Construction,i think) livery, is pictured here passing through Slateford station and running wrong line to gain access to the Edinburgh sub line with an unidentified test train working on (date unknown,approx early 1990's).
Please note the absence of overhead wires and equipment in this shot compared with other pictures from this location (I,Ross Aitken is the person standing in the shelter).

Photo: Scott Aitken. Scan: Ross Aitken (aos@cableinet.co.uk).