With some interesting PW work going on, note the trap point and special rail presumably to stop runaways falling onto the work. Estimated date as Vic Smith says: 'possibly 15 June 1957. Check the photo taken in reverse direction showing corrugated sheet fencing, redundant track & equipment: 60021 1957-06-15 Hadley Wood.

The “interesting PW work going on” would be to the left of the photo – construction of the second parallel tunnel bore.

Could they be removing sandtraps similar to those at Welwyn?' Thanks Vic.