Conkers - there were hundreds of these - my husband sheepishly confessed to 'disappearing' our son's huge conker collection a couple of years.
The conkers were jet black so I guess they were composting albeit slowly.

Egg shells - I always threw these in the compost in halves, after having cracked them. Now I know why Steve Tinling, THE Compost Guru recommends chopping things up. The halves were intact. In future I shall make sure that these are crushed up well before going in the bin as well as chopping other items down to size.

Monkey Nut Shells - I don't remember even buying these but after two-three years they looked perfect.

Compostable Cutlery - I was annoyed about this as I had paid over the odds for these and provided them to my children's school for the summer fete a few years back. I had then taken all the used plates and cutlery home and put them in the compost.
I am not sure how long they are supposed to take to break down but even a couple of years in the compost bin had made no impact on them.

Compostable fruit and veg bags from Sainsburys - admittedly when I started to pick these out of the compost they broke up very easily.

Tea Pigs - those funky teabags - I came across lots of these, the tea was no longer in them but the bags were as good as new.

A loaf of bread - eh!?????

Having now spread the compost over the raised bed in the back yard and picked out the bulky items, I still keep seeing egg shells and flaming conkers.
"Be sure your sins will find you out" I said to my husband as he tried to hide some of the conkers under the lavender bush to stop our son from discovering them and putting two and two together.

I realised that I am a bit too gung-ho when it comes to composting.
I throw everything in the compost bin, including loaves of bread as it turns out, in the belief that it will all break down and now I jolly well know that not everything does compost or at least some things take a bit longer than a few years!