Where is it?

I stumbled upon this double slip in concrete this afternoon.
Where is it?
For those who know, what's its use & history?
Answer via the comments below .....

Following a correct answer, this post has been extended with added railway items, especially E1 / J72s, courtesy of Alan Thompson .....

J72 68742 on Newcastle Quayside, but not on a double slip
(photo Charlton collection)

Spillers' Wharf with J72 69024 shunting between road vehicles
(photo Alan Thompson)

A little further east, 68738 is heading a train of ?? with the shunter aboard, while under the waggons .....
(photo Alan Thompson)

..... it's the double slip, here with 68245 passing, again with on board shunter
(photo Armstrong Collection)