Unusual thing happened on Friday - my Northern line train (Bank Branch)
announced that it was terminating at Kennington, which I've not seen before.

Question is... what happened to it? It left in a southbound direction, and
AFAIK there's no 'normal' way for it to reverse or get on to the CX branch
loop.

I also noticed that three cX trains in succession also terminated there, and
came up with a wild theory that the bank train might've travelled beyond the
junction, then reversed northbound back up the CX branch, and then gone
southbound again round the loop...

Or possibly it ran empty to Tooting Broadway/Morden?

Any ideas?

BTN