Very long shot but I've been trying to find it for years. It was read to the class in infant school in 1981, but I seem to remember it had an old board cover so it could be much earlier.
It's not a picture book.
The story was about a boy who somehow came by a (baby?) elephant - it might have been a birthday gift. The boy and his elephant got involved/kidnapped by evil-doers (possibly a circus) and the last bit I heard was them being transported away on a train, in a cattle truck.
For some reason the teacher didn't finish reading the book and that's all I can remember (and some of it might be incorrect).
Any suggestions however vague would be very gratefully received!