If, as you suggest in your OP James, he was the first one home he would have had very few visual clues to follow in the black hole that night.
2.50am. Home early perhaps? Moon not yet up. Operation planned for an expected slightly later moonlight return? Airfield still preparing the last flares?
Gooseneck flares are good for marking a runway location and direction but give very little glidepath information. With conventional lights either side of a runway you have a shape to aim for. If that shape is long and thin you're too high, short and fat and you're too low.
With a single line of flares in complete darkness all you've got for glidepath is the apparent spacing between flares (which may not be perfectly even anyway) and the apparent length of the line (which may be compromised if the runway isn't level - common in wartime grass strips). Difficult to fly a stabilised approach with no other clues, and so easy to sink below the ideal glidepath.
It all reminds me of some good flying advice:
Let someone else have a go at it first and follow them if they make it safely!!