I needed the Northern Line last week, on the afternoon of the London Bridge attack. The City branch was - understandably - non-stopping at London Bridge. But the whole of the Charing Cross branch was closed at the same time (hence making the crush on the other route pretty bad), and I could find no explanation for that closure. Was it in any way related to the London Bridge incident? (In which case, why shut that branch?) Or just a coincidence, but without any announcement of why?