Hi Nyall, > Which version? There was a bug in 3.0.0 (fixed in 3.0.1, by > https://github.com/qgis/QGIS/commit/dff31a4a19 ) which meant the ogr > provider held a reference to a layer for 60 seconds after it was > removed from a project. my fault again. It's on 2.18. So in Q3 this issue is fixed? Thanks! Matteo