I was twelve. During morning break at school I 'discovered' I had started my period when I went to the toilet. I was mortified as I was totally unprepared and had no money for the vending machine. We had been given 'the talk' as school some months before along with a booklet which I took home to show Mum but even then she didn't enlarge on the fact or explain where I could find pads at home - I had an older sister. Another girl, who I hardly knew, lent my two shillings to buy a pad the size of the Isle of Wight. That was the start of a great friendship. I told Mum when I got home and she instructed my sister to tell me where the pads were kept at home.
The experience made me adamant that my daughters would be well prepared for their first periods and I have never understood why the subject was, and still is, taboo amongst some families etc.