Saw these creatures in my garden today and all attampts to identify have so far failed. Can anyone help?

Thanks

Caterpillar of some kind I'd guess. But .........?

This is a bit of a puzzle to me. What it looks like you have is a pair of mating beetles, the male is on the right.
The strange thing about it is that normally you would get two actual beetles mating together and then an egg would be laid either underground in in wood and then a larvae/grub would hatch, but yours looks like the female (on the right) does not form into a normal beetle (a bit like the some of the moths in which the females have no wings).
As to which species of beetle it is i am not sure, it looks a little like a leaf type to me?

Rather than beetles mating, could it be a beetle giving birth? I know some beetles give birth to live young but have no idea what size the young would be. There is certainly a large size difference between the two.