There was a broken down train at Plumstead, so all Thameslink services diverted via Lewisham and Bexleyheath.
All Thameslink drivers that sign the route to Dartford via Abbey Wood also sign the diversionary route via Bexleyheath - this is Gillingham (GH) drivers and Luton (LU) drivers, as well as the hired Southeastern Orpington drivers who obviously sign both.