One of the reasons for the withdrawal of this service is the redevelopment of London Bridge station. While they are changing the platform layout, there will be less capacity at London Bridge - indeed there is the possibility that they might have to change our services as well in the near future, but Southern are being very careful not to make any promises at the moment.

The reason that the SLL was chosen to be cut is that it was a relatively under utilised service. That is not to say that it was unpopular, just that all the other services going into London Bridge were more crowded (and over 100% capacity). It was originally planned that the service would be replaced by one from from Victoria-Bellingham instead of Victoria - London Bridge, but TfL decided to trade that for the money to build ELLX2 - the upcoming service from Highbury & Islington to Clapham Junction via Peckham Rye. A fuller explanation can be read here.

Do not confuse the SLL with the service from Victoria to London Bridge via Forest Hill will still run.