This is a BR Publicity photographs designed to be handed out and used for promotional purposes. The wording on the back says roughly PR&PO British Railways Please Acknowledge.
This photograph is particularly unique in that it shows a Class 31 at Mallaig on 11th July 1958 when on trial in Scotland. [See image 24644]
PR&PO British Railways (Douglas Blades Collection) [11/07/1958]

Looks like rain... The gathering storm, Mallaig station, 27 September 2005.
John Furnevel [27/09/2005]

45407 runs round its train at Mallaig on 18 June after working in on the afternoon Jacobite service from Fort William. Captured in a quick dash from the ferry terminal before booking in time for the Skye ferry.
David Pesterfield [18/06/2013]
All photographs of Mallaig