Loads of other replies while I was typing mine (if it looks like I hadn't read them!). The muntjac deer idea looks promising? At least two sites had a nice photo but no indication of size, but seems about right (having finally found a site mentioning size).
Good luck with the camera. I have what's really a wired birdbox camera on duty outside - usually motion-detecting the hedgehog. Though a visiting pheasant managed to video itself the other day!
Posts
https://practicalhome.uk/identify-animal-poo/
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
http://www.newforestexplorersguide.co.uk/wildlife/mammals/deer/field-signs/droppings.html
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.