My earliest memory is of a day I jumped into a pond/fountain thing at a stately home somewhere in the English countryside.
For those who don't know, a 'stately home' is a big posh historic English country mansion, many of which have had the grounds opened to the public, to be visited freely (or for the price of an admission ticket).
A bit like the picture below.
I jumped into a fountain, similar to that one. My feet and little legs got wet, and then I cried. This is my earliest memory.
I recounted the memory to my mum not long ago. She knew the day well, and was amazed I could remember it.
The funny thing is that the logical reason for me being able to remember it so well is that it was probably my first ever traumatic experience. Oh, the trauma!
I also have a very old memory of a day we went on a family holiday somewhere (possibly the east coast of England) and stayed in a caravan. I remember waking up and singing a song about butterflies to myself, while staring for a not-insignificant amount of time at the old-fashioned brown flowery patterns that had been used on most of the upholstery. It's a very vague memory though, has a sort of deep, wispy feel to it, like a whole other life. I'm amazed it still sits in my brain, actually. Brains are fucking amazing.