And I know this is going to sound suspect, but it’s completely true and to be clear the young lady is not vaguely related to me.

So, brother and his partner are round my house and his partners daughter (just finishing A levels) was there too (daughter from a previous relationship). Pretty rare she came round as she’s old enough to do her own thing. I’d never really spoken to her in any depth, but that day we got talking about her college stuff and one of her subjects is environmental science. Ended up chatting away as in a keen forager. Fast forward two weekends and as it’s late summer I’ve offered to take her out for a nature walk, for species ID and so on. We’re in some fairly unused woodland near my house and chatting away - nothing weird - when she says she has to pee. I tell her it’s always quiet and just find a convenient tree to pee behind, which she does. Of course I turn away, make nothing of it (but it’s clearly a bit hot) and then she asks if I need to pee too! I say yes (I didn’t really) and she says something like “go ahead, I’ve seen it all before”. She’s pulled up her jeans and walks round and looks at me, so I unzip and pee in front of her. She immediately says that it’s a nice view or similar - and I reply that she’d better not keep staring or I won’t be able to go. She asks why, and I say “well, you can’t pee if you’re hard”! That seemed to be what she wanted, and as I’m shaking myself she puts her hand on it. Instant erection! She starts fondling me and at the same time unbuttons her jeans again, pulling them and her panties slightly down. We end up masturbating each other in the woods for about 10 minutes until we both came. It’s never happened since, nor will anything else I suspect, but it’s a great memory.