It surprises me that the ground record was set in 1928 at in excess of 47,200 and yet by the early 1960s and without any significant changes in the stadium and the capacity was limited to 42,000 - it felt that we were packed in like the proverbial sardines. I do remember one particular occasion which i think was an FA Cup replay against Birmingham City when the gate at the Filbert Street Stand/ Popular Side intersection was damaged that there were maybe 44,000 on the ground taking account of those who got in without paying.
The ground did have a tremendous atmosphere particularly in the days when it was all standing (except for the upper Double Decker and the old main stand.). I think there was a bigger roar then when City took the field than when they (rarely) score a goal at the Walkers.