Several years ago, ds1 and I were hanging the washing out in the back garden early in the morning. ds2 was at crawling stage and closed the back door and shoved the extra-secure bolt down. There was no way he would be able to pull it up again, or even understand what to do.
ds1 and I had to run down the back alley, round by the main road to our neighbour's house, beg her to drive to dh's work to pick up his keys and drive us home so we could get back in the house.
All in all it took 45 minutes and ds1 and I were in our pyjamas!
ds2 was still in the playroom. He'd crawled away from the door and was playing with the twangy thing that stops the door from banging into the wall.
I suppose this little story shows how I should have taken both dc outside with me, to avoid what was a fairly fraught 45 minutes.
But a couple of years later, while I was watching, ds1 had a freak accident and fell out of tree that he climbed on a daily basis. He landed on his face, ripped it open and even after extensive surgery is going to have a noticeable scar for life. I was there and watching.
All I have learned from life is that you must assess potential risk, but remember to have a life at the same time, because the worst accidents can happen even when you have been risk averse.