An obstruction at Blackheath has halted Southeastern services.
At the time of writing (2:30pm) services have been blocked for 30 minutes. Southeastern state buses can be used with rail tickets and trains are diverted:
UPDATE – Trains remain unable to run from #Blackheath towards London because of an obstruction on the track. You can use tickets on London Bus services at no extra cost between Dartford and Lewisham to help you complete your journey
— Southeastern (@Se_Railway) May 4, 2019