According to Molvar:
"Barry Magee
According to Lydiard could never in his career run faster than 58 in a 440.
age 18 before Lydiard 4:50 mile and 11:00 2 mile
age 19 first year 9:50 2 mile
eventually Magee got down to 8:45 2 mile, 13:38 5000, 28:50 10000 and 4:07 in the mile. Amazing for a guy who couldn't run faster than 58 for a quarter. He was ranked # 1 in the World in the 10000 and # 2 in the 5000 by Track & Field News. Also won bronze in the Olympic marathon."
You've got to take into consideration that the tracks in New Zealand in the 50s were mostly grass and could get fairly muddy, but dropping 43 seconds in the mile as an adult is an incredible accomplishment.