Vicky Ewan: 18 and the world is my son's oyster - but home will always be where the heart is

One of my offspring, the fourth in line to the throne, achieved a milestone recently - the first of our sons to do so.
It still fills me with wonder, when I pause to give it due consideration, that a woman can carry within her, sustaining it and giving it life for 40 weeks, something so Other: a male child.
It's an everyday miracle, perhaps, but no less astounding for its prolificacy.
Generally speaking, those baby boys are destined to grow up and become men, and that's what has just happened to our elder son: he, according to the laws of our country and his own proclivities, is now a man: a fully-fledged, legally enfranchised, beer-swilling adult.
What makes this development even more momentous for me is that for a long time I thought I wouldn't (or, perhaps, couldn't) have boys; our first three children, beautiful daughters all, set a precedent in my mind from which I lacked the imagination to deviate.
When the happy news that I was expecting another child revealed itself, although, as ever, I had no preference, I was fully geared up for a fourth baby girl, believing (smugly and wrongly) that I had this baby malarkey sussed.
I had preserved my most recent offspring's early-life clothes, floral fripperies in pinks and pastels, convinced that I would need to lay my hands on them again. A pretty name, chosen to complement her sisters', had been agreed for a fourth daughter. I was placid as a benign bovine in my role as girl-mother, fully accepting that that was who I was.
And then along came this young pretender, forcing me to re-examine motherhood from a different angle. From the outset, he was a different kettle of fish. We are all familiar with the affectionate stereotype of grumpy old man, and most of us can probably identify a candidate or two who fits that profile (naming no names, naturally); well, for the first seven months of his life, my infant son was the miniature version: sleep-averse, cantankerous, and curmudgeonly, his dear little face was set in what seemed a worryingly permanent scowl.
Thankfully, that fog finally lifted, and he became something of a joy: sweet, affable, and swift to smile. Basking in the attention of three (usually) doting sisters, he bounced through his days as though he had springs in his tiny shoes. Gazing at him fondly, with his long butter-yellow curls flouncing about on his shoulders and a grin permanently affixed to his face, my husband and I used to describe him as being generally pleased with life.
So disarming was he that he would regularly persuade everyone about him to draw pictures of castles - his absolute favourite thing - with no apparent effort whatsoever (and no apparent talent whatsoever, from many of us). His innocent penchant for these masterful buildings led to our family frequently visiting castles on days out; language such as 'tessellation' and 'turret' regularly peppered our vocabulary.
From a young age, he toddled about the house, singing at the top of his voice and performing dances that defied the laws of physics and anatomy. A friend of mine, whom we had chosen to be our son's Godmother, remarked during a phone chat that, when I spoke about him, she could invariably detect a smile creep into my tone.
And the love was mutual: another friend, in whose arms he lay one day, told me that his breath quickened at the sound of my voice; these are the moments we treasure, the seconds that cancel out seven months of grumpiness and every sleepless night.
He was a beautiful little boy. As he grew, his personality established itself in subtle but definite ways: he was expressive, musical, artistic, and academically able enough that he could satisfy his teachers and please his parents. He had a certain sense of self, and a steely core running through him that still takes us by surprise on the rare occasion that he reveals it - usually in direct contravention to whatever it is that we would like him to do.
We know that, like his sister before him, his head is filled with visions of a future in our nation's capital: his heart is already there, and the rest of him bides its time till he's free to go. At 18, the world is his oyster; I just pray that once he's gone, he'll find his way back to his seaside home eventually.