When we recently redecorated my son's bedroom we left masking tape on the window panes for a little longer than the recommended 2 hours - well for about 4 days, actually.
When we came to remove it we found that it had left a hard residue on the windows which has so far proved impossible to remove.
Can anyone suggest a way of getting this off?

When we came to remove it we found that it had left a hard residue on the windows which has so far proved impossible to remove.
Can anyone suggest a way of getting this off?