Mum's white satin bra. I'd have been about 13.
Mum, Dad and my brother had gone to town and I was alone and bored.
Tried it on from her underwear drawer. Only had it on for a minute when I paniced about them coming home finding me.
In the panic, I couldnt release to hooks and fumbled for a good 2 minutes before turning it around on me and un-doing it at the front.
5 minutes later, when I realised they'd be gone for hours, and had only been gone for 30 minutes, I was back in the drawer trying the matching knickers and the bra.
Then the matching suspenders too and some tan stockings.

So the very first was a bra, but in the same day I was up to full underwear.

The next saturday I went a lil further, more so the week after... and the rest leads me here