In the very early days of HS1 SE services, I seem to recall Javelins running empty on a Wednesday only (??) via Fawkham to Swanley and then coming back, to have a route refresher. The diversions into Victoria could be done as the drivers would ride in a cab of a conventional train between Swanley and Victoria. They also signed via Dartford and Lewisham so that a service to London could be supplied.
My understanding now is that no such service can be provided as diversionary knowledge has lapsed (too expensive and bothersome). The power, as I understand, is also either off or somehow defective on the connection as well.
Would be interesting to see if the proposals to ‘recycle’ that section come to pass as there was a desire to have a Victoria - Bromley South - Ebbsfleet service. I couldn’t see a business case, but then again I’m not some sort of visionary politician with a majority to maintain.