I had all but given up on Jonah ever mastering the art of walking, when lo and behold he took his first steps.
He had been dashing around using his walker, when suddenly he just let go and launched himself into the brave new world of walking tall.
I had thought that by the time I got to son number three I would be blasé about this seminal moment in a child's development, but I wasn't.
I had tears in my eyes when I saw how proud he was of his first faltering steps. I whipped out the video camera to record them for posterity whilst yelling down the phone to his dad about what a clever boy he was (Jonah, not his dad, you understand).
I still remember when both of my other boys first walked. Jacob teetered along the upstairs hall in our old house, while Max walked across the living room of the same house, hand held aloft as if he were still holding on to some invisible steadying hand.
Now I just have to wait for Zachary to catch up and I will have the full quartet of memories.
I am amazed at how it has changed Jonah as a person by upgrading from baby to toddler.
He is no longer constantly contained in a pushchair and can now wobble around quite quickly. This is lovely as it has made him far more a part of the family as he toddles after his big brothers, but it's also terrifying given his complete lack of regard for personal safety.
Nothing has ever been too sharp, too hot, too fragile or too dangerous to escape his attention, and now he's upright a whole new level of hazards have opened up to his reach. I am afraid, very afraid.