MichaelG
If UK – but refer to posting by Rik Shaw above at 18:01:37 suggesting French origin:
The headcode the locomotive is carrying: two white diamonds, one centrally, one on right upper position would conform with a LSWR locomotive routed:
Salisbury, Southampton West & Portsmouth via Netley.
Dorchester & Bournemouth Central.
Waterloo & Virginia Water, via Main line
Refer No:24 here: **LINK**
However the locomotive appears to be additionally carrying a single lamp in the left upper position.
(May indicate number 44 on the schema.)
Further to my earlier posting don't think that Highland Railway used 'routing indicators' of this type.
Might be worth considering LSWR locomotives??
The large cab-front 'look-outs' are quite distinctive, and the lining appears to be a lighter colour surrounded by a darker colour. The boiler hand-rail running over the top of the smokebox-front and sand-boxes built into and ahead of front driving splashers might help identification. Certainly looks like a 4-4-0 wheel configuration.
Regards, Phil