One day, when our first son was about three and a half, I made a horrifying discovery in the utility room. There's no way of putting this politely – it was a fresh mound of poo in the middle of the floor!
"Why is there poo here?" I pleaded with our youngster. "Why didn't you ask us to help you use the toilet."
If, as it appeared, he hadn't learned how to use the toilet properly by then, he had certainly learned to fib, because he brazenly denied being responsible.
The weird thing was that he had no mess on his trousers or pants and looked genuinely bemused as to how the mystery faeces had got there.
Quite what went on still puzzles me to this day, but there's one thing I'm certain about - dealing with my children's daily bodily functions is one of the more exasperating aspects of being a parent.
Take potty training. It's one of those developmental hurdles that you dread when you've got little ones. Our first son actually learned how to use the potty quite quickly but, second time around, our attempts seem to have ended up in a total mess.
At nearly three our younger son is totally resistant to the idea. Now I fear we have totally put our foot in it by repeatedly stopping and starting the process over the last six months.
We're well aware that you're not supposed to try and force potty training on your toddler until they seem ready, yet we're also aware that the older he gets the more difficult it may become. It seems to us that he needs a bit of a helping hand as he is clearly fed up with wearing nappies, regularly demanding to don pants in the morning, just like his brother.
Yet he just doesn't have any interest in using the potty. And we're fed up of trying plans, by the likes of Gina Ford, that promise to train your child to be dry in just a week. For us they have failed dismally.
We're not alone in our frustrations. Studies show that children are taking longer and longer to learn toileting skills. Alarmingly, a 2012 survey of teachers shows that rising numbers of children are actually starting primary school without being toilet trained.
In some parts of the world however, like Asia, parents are successfully potty training babies before they are 12 months old. A UK survey found that one in six mums feel under pressure to potty train their children and push them to be dry.
But for those of us who want their children to get on with ditching the diapers the advice out there isn't always that helpful. The NHS website, for instance, advises: "Do it over a period of time when there are no great disruptions or changes to your child's or your family's routine."
Just when, I ask, given that we both work and have one son at school and another at nursery is there such a time?
So far, we've followed all those handy hints to the letter, like 'Leave the potty out so that he can get used to the idea.' Well we've now virtually got one in every room. I'd worry about accidentally kicking them over with something offensive inside if my son had any interest in using the damned devices.
As far as he's concerned they are simply there to use as footballs or extra parts of his plastic tea set!
There's a plethora of other advice. 'Let them choose their potty' for example. But neither special musical potties or handy step up stools have made our son more keen.
Official advice is full of warnings not to upset your child by exerting too much pressure. So my son sits stress free on the potty, does nothing, then prefers to take himself off and do a wee behind the curtains instead.
Each time we have a few straight days at potty training we eventually give up, straining under a mountain of washing and deciding to let the floors and carpets recover for a bit.
One guide advises letting your child see you going to the toilet to get used to the idea. I've tried this approach. But when mine happily comes into the bathroom to watch me relieving myself you can almost see him thinking. 'Oh dear, when will Daddy learn to use a nappy!'
We've stayed calm, tried to make toilet training part of the routine and been encouraging without giving too much praise, just as the child rearing gurus tell us.
We have also avoided giving sweets as a reward, as apparently this can store up problems. But I'm sorely tempted. At the moment I'd buy him a lifetime's supply of chocolate if he would stop spoiling his smalls for a day.
Of course the main problem may be that he just doesn't know when a bowel movement is coming. But we're increasingly worried about just when this might happen.
I'm slightly reassured by a study conducted at the Children's Hospital of Philadelphia which found that there was no benefit to potty training your child under 27 months and that results were faster for slightly older children.
Sadly we haven't yet been able to help add weight to this research.
The NHS website continues: "When the time is right, your child will want to use the potty and they will just be happy to get it right."
I think we'll be holding a party when he does or perhaps a gleeful bonfire of the nappies. After getting through approximately 5000 of the things, I certainly won't miss them.
More on Parentdish: 5 things you learn when potty training your toddler