Full steam ahead

It could hardly escape the attention of an inveterate railway enthusiast! For a few days scheduled trains on the famed Settle to Carlisle line, linking Yorkshire and Cumbria in northern England, have been hauled by the magnificent steam locomotive Tornado. 

What came as something of a surprise was that this exploit would have a German angle.

The video shows that behind Tornado there's the inexplicable presence of a Deutsche Bahn diesel-electric (Class 60099) locomotive lending its power to the train. 

How odd!

[Update]
Perhaps not so odd after all, when explained by this link found by my sister Pippa!