Several years ago I witnessed the "Peoples Express" 747-100 shortly after its T/O incident at LGW.
It came overhead my location at around 2-3 thousand feet on its way back to LGW. It was still dumping and the fuel vapour could be smelt within a couple of minutes.
Normally (if you can call a fuel dump normal ) it would have been over the sea, or at much greater height or both, but circumstances dictated otherwise in this case.