I've been trying to recall when I got it. My copy says it is the 1978 impression, so I must have been at least 7 at the time. This was before I started buying DWM (age 11) and I'm fairly sure I had The Making of Doctor Who "some time" before I started buying DWM but after I'd bought Web of Fear - mind you "some time" in the mind of a child may not be that long.
no subject
I would guess age 8 or 9, but its only a guess.