I can see where you are coming from but I am 99% certain that actually the apron was still there but just covered in a light covering of earth held in place by thin strips of wood for the film set, as this was the location of the Nissen huts that were erected as part of the film set.
I bunked off work to take these.
When the film was made the tower was given a makeover with glass being put back into the window frames but it didn't take long after the site was vacated for the vandals to pay a visit to the tower once again.