Anyone know what happened
 

I think the question is answered on the first comment.Illuminated steam. Looked impressive though.
Stuart

Very spectacular! I have read of blowback upon entering a tunnel in earlier steam locos but obviously this was not the case here.

I was watching some old you tube films of the last days of steam yesterday.

There were several times when drifting steam seemed to intensify the firebox glow and give the appearance of a the cab alight.;)