I wonder if the stone was placed closer to the tracks possibly where the locomotive crashed. There is a small "wooded" area on both sides of the track at this location:
52 57 10.9 North, 08 26 08.7 East
52.953014349487255 North, 8.435752763880485 East
https://www.google.com/maps/place/52...43!4d8.4357528
Halliwell had joined the squadron in late March flying his first mission on March 22.