A4 at Crewe

[trainspotter1948]

Gentlemen,
En route from Crewe to Liverpool in the morning a few weeks ago I spotted this A4 in the Heritage Museum, but was too slow to do anything.
On the way back, it was getting dark and the train was just slowing, but I got a few poor images of which this is the best.

https://www.dropbox.com/s/olj5wtr1zgbwi ... 8.JPG?dl=0

I am almost certain it was Union of South Africa.
Any ideas on what it is doing there and for how long?
I'll be back in Crewe on foot on Wednesday, so I might pop along and have a shufty.

Alan