We did sigh with joy at the arrival of a royal princess - but, mostly, we sighed with pity at the sight of Prince George being taken to meet her. Little did he know his apple-of-the-eye existence was about to go pear-shaped.
It's a trauma that few firstborns can escape. BBC newsreader Kate Silverton spoke for many parents this week when she admitted to feeling guilt at neglecting her three-year old, Clemency, after the birth of her son, Wilbur. "I wasn't prepared to feel so protective of him," she said, "sometimes even at the expense of my daughter's feelings."
My firstborn made the same momentous journey as Prince George, tottering along to the Lindo Wing with his father to meet his new sibling, blissfully unaware that a serpent had entered Eden.
We'd tried to emotionally prepare our son for this fateful day. We suggested the baby in my tummy would one day be his friend. Oscar's response? "I hit baby with stick! I smack his bot!" When they finally met, I positioned Baby Conrad in his cot, so that when Number One Son entered the hospital room, I was free for a cuddle.
Following the birth of their daughter, the Duchess of Cambridge and Prince William wisely enlisted the help of Carole Middleton, whose focus is reportedly "on George, rather than the new arrival". We also attempted the cunning ploy of calling in the mother-in-law. Sadly, it failed to placate.
When I returned home with the interloper, an array of fawning relatives were in attendance - not for Conrad, as neglected that day as our two cats - but for firstborn Oscar, who received as many presents as if it were his birthday.
After 20 minutes of fuss, Oscar abandoned his new wooden fire engine, and stood over his sleeping brother. Then he said to me: "Are you his mummy, too?"
If Conrad lay on his playmat, Oscar pretended to trip over him. If Conrad cried, Oscar would enquire, in mystified tone: "What's that sound????" Plainly, he was in denial. But is it any wonder that when the firstborn is, as Jane Austen might put it, "so cried up", the shift of the parental gaze to a squalling rival feels both devastating and unacceptable?
It is no surprise at all to Elaine Halligan, London director of The Parent Practice, which runs parenting workshops. She says: "Firstborn children almost always feel naturally displaced when a new baby arrives. Parents imagine a baby's a bundle of joy for the whole family, but the firstborn's world is turned upside-down."
Often parents can't bear to acknowledge this inconvenient truth. A neighbour recalls her nephew, two, "vying for his mum's attention" after his brother's birth.
"We were in the garden and he was digging in the flower bed, and he kept saying to his mum: 'I'm a good boy. I'm working so hard, aren't I?' My sister was breastfeeding, not really listening. I felt so sorry for him."
The chances are, however, the mum was listening, but was struggling with a double whammy of guilt. It's what Silverton describes as the rollercoaster of conflicting feelings - that in some way you are letting both children down by not attending your newborn's needs as you should and not being the same kind of focused mother you were to your eldest before their sibling arrived.
Keeping the baby physically safe is a priority, of course. But beyond that, says Halligan, "rather than trying to persuade the older sibling to love the baby, allow them to express their natural feelings of resentment and jealousy.
Give lots of reassurance, that they're still loved. Set time aside, even 10 minutes, to give them exclusive attention. Notice and comment on all good behaviour. Rather than brush negative feelings under the nursery rug, Halligan advises: "Let your older child know that whatever they're feeling, it's OK, and it's OK to tell you about it. Say: 'It's really different for you, with a baby sister. You're used to having me all to yourself. It looks to me as if you may not like having to share me.'?"
This approach is not instinctive to parents: we hoped a second child would complete our family, not destroy it. Yet, if handled sensitively, that initial sibling resentment will diminish.
I know this, because when the much-despised Conrad was two, he climbed a tall ladder propped against a garden wall. Only Oscar's screams alerted us to his plight. My happy feeling: when they no longer wish each other dead, the day of sibling friendship and devotion is surely close at hand.
The Daily Telegraph