In today's budget speech, George Osborne announced that he was cutting the duty on beer 'by one pence'.Oh, no, you're not, you Bullingdon oik.
'Pence' is the plural which you would use if there were more than one. When there is only one, you use the singular, which is 'penny'.
It's a shame your very expensive education didn't make sure you left university aware of that.