Thameslink train at Orpington Station today

Today I saw a Thameslink train at Orpington Station at around 7.45. Nothing strange about that you may ask, except this was on the railway bridge beyond Orpington (where they normally terminate) on the line to or from Sevenoaks. Being stationary on the bridge I could not see which direction it was travelling. I've looked on RTT, but could not find it. Any idea what it was?

(I don't think that it was connected with the person hit near Hither Green - this was a bit earlier than that.)

Thameslink trains routinely work on the main between Sevenoaks and Orpington. Late running Sevenoaks trains are often diverted this way between Sevenoaks and Bickley to make time up, and ECS moves to/from Sevenoaks/Orpington/Bellingham etc. If you saw it stopped on the viaduct it was probably an ECS move waiting for the route from the up to platform 5 to access the sidings.

They often divert that way during engineering works when the line via Bat and Ball is closed