As a Gateshead locomotive for most of its career 55011 (D9011) "THE ROYAL NORTHUMBERLAND FUSILIERS" would not have been one of the cleanest members of the class.
Indeed Gateshead was not renown for using any washing facilities, however, by the time this shot of 55011 was taken, on the 6th April 1981, the loco had been a resident of York shed for nearly two years.
The filthy loco is seen  at the head of the 1A28 16:30 Hull - King's Cross service at Hull.