I had an imaginary friend til I was about 5. I'd only see him in the henhouse. We'd go there at night to shut the hens in to keep them safe from foxes, and my dad and I used to sit in there sometimes as you could see what we called "glow worms" - not sure what they were but that's what my dad called them. Maybe the same thing as a firefly, I dunno. (Not seen them ever again in my life just in that wooden hen hut).
And then I'd often go on my own or stay after we'd herded in the chickens, and just sit in there to watch the glow worms and meet my imaginary friend. I knew he was imaginary because my parents told me he was. I only saw him there, in that specific place. Thing was, he was probably unusual as little girls' imaginary friends go, as he was a teenage boy (I have no idea of the age just that he was older than my brother who was 5 years older than me). I'd guess I'd have stopped talking about him because I would have been laughed at (esp by bro).
Another weird thing was he was "foreign" and somehow different. Bear in mind this was 1960s' rural Yorkshire where the biggest "foreigner" usually was someone from 5 miles away. I doubt I'd even have had that word "foreign" or concept, if it hadn't been for the fact that for some time there was a little French kid in my class at school. He had one of those double barrelled names I forget but like Jean Paul, and I remember thinking my imaginary friend's name reminded me of his.
My only real vivid memory of imaginary friend is the last time I ever saw him. I'd be around 5. He said to me I'd never see him again. Not ever. I was really sad. (Not a lonely child - although I wanted to be. Probably undiagnosed autistic spectrum, but again in the 1960s we had no concept of that. So I was happiest alone, playing by myself).
I should add my "garden" was in fact an old orchard, an acre, with drystone walls round it - but no wall at the end where it just let into a field. So technically, anyone could just walk in there, if they wanted. And it could indeed have been an actual person. Only it wasn't or I didn't think he was "real". Scary thing is, a teenage boy could have just walked in there every night - it was out of sight of our house, down the bottom of a steep hill, behind a load of trees. Thing is, in a village everyone knew everyone and even as a 5 year old, you'd recognise all the teenagers in the village as being so and so's big brother, or someone or other's son. There was nobody we didn't know.
I only ever saw him in the hen hut. He wasn't scary. He was kind and my "friend" and I enjoyed our chats.
30 years later, land was sold and whilst digging foundations, the builders hit two Roman stone sarcophagi. Meters from this part of our garden. Neither were teenage boys - although one was a young girl of a similar age. Thing is, these graves will have gone in along the line of a lost road that will have crossed our orchard. So there were no doubt other burials that hadn't survived because they didn't have the fancy stone coffins... Other weird thing was, my grandad had knocked down an old farm building quite near that place where the burials were found and maybe 2m from the henhut. My whole childhood, my parents just left that pile of bricks and pantiles and rubble there. When I was about 10 or 11, my friend and I used some of it to build an ever increasing complex of buildings (just a couple of bricks high, and using pantiles as rooves) which we called our "Roman villa". (As a burial area there'd have been no villas there, of course, but it is thought that with high status coffins made from millstone grit there might have been mausoleums or at least, large gravestones).
For many years I thought they were military graves but someone here pointed me to the archaeological report, which we finally read for the first time last year. The male a bit older than my imaginary friend but had healed injuries on his skeleton not inconsistent with being military, possibly.
I told this story years ago when we still thought they were military graves, on a now gone, closed, forum. Another forum member was the sister of a well known TV sci fi series writer who may have used elements of this to tell a story (also may just be coincidence).
Still wonder why he felt the need to say goodbye and that I wouldn't ever see him again.
Tldr: my childhood garden was a Roman graveyard. I might have met a Roman (no Latin was spoken lol).