Do they run Charing Cross-Cannon Street Services?

[Leuvenn]

I work near both stations and I'm aware that, before the District, Circle line, there was a service between the two stations.

Does this still occur, albeit only once a week as a parliamentary service?

If not, what purpose does the curve from Waterloo East to Cannon Street serve?
Is it a relief line or a relic.

I'm curious

 

[yoyothehobo]

Thread from a few months back

Link above to previous thread on the topic