Dear Kate, Here's what to expect when 3 become 4.

Royal or not, mums are mums. So listen up, Kate. This is what it’s like with a second child.

Hi Kate. I heard a whisper you might be having another baby. Let me be among the first 100,000,000 to congratulate you. And just in case no one else is going to offer you advice on what life’s like with a second child, here are some thoughts from me. Mum to mum.

You may worry that you could never love a second child as much as the first one. When my daughter was little, I loved her so intensely that I honestly believed it wouldn't be possible to feel the same way about another child. In fact, one of the reasons I had a second baby was that the intensity of love for my daughter scared me. When baby number two arrives, you might not feel the same love immediately. The new one is just a little baby, while the older one has such a personality. But that baby will grow and you will love them just as much, for the person they are.

You won't get as many presents. (Oh, wait, Kate, you will, because your baby is royalty, but I didn't.) With the first child, it's a massive haul. More clothes than they could possibly wear. Twenty pairs of crocheted booties that fall off as soon as you put them on. Handmade bibs. A patchwork quilt that's just too beautiful to use. You will feel overwhelmed and almost brought to tears by people's generosity. With the second child, it's like, "Hey guys, I just had a baby! Where's my free stuff?" You may find yourself actually having to buy baby clothes.

You will feel guilty that you're not giving your second child as much one-on-one time as your first child. You can't just lie on the floor and gently shake a rattle at your baby without your toddler leaping on your back and screaming, "Horsey ride!" You can't sing, Twinkle Twinkle Little Star to the end because that gives your older child enough time to get into the pantry and open a bag of icing sugar. But that's okay. As long as the new baby is being held, and listening and watching, and feeling like they're part of the action, they're still learning. (I hope.)

You need to make an effort to record things. You will probably find your first child's firsts are burned into your brain. First word, first step, first poo in the potty, etc. Then the second child comes along and things start to blur. Write things down. Get the camera out and take photos (although not of the poo in the potty). If you don't, your younger child will run a massive guilt trip on you. I have a long list of my daughter's first words all written down, in order (bath, ham, pub, etc). But last night my son asked me about his first word, and all I could say was, "Um, I think it was 'more'." Sorry.

Your heart will melt when you see your kids playing together. My daughter was not interested in my son when he was a baby, but once he was walking and talking, they started to invent their own games, like "Slip Slide Dangerous" and "Collection Of Bruises". Seeing your two kids chattering together, their heads close, absorbed in their private world, is wonderful. And it means you can sit and have a quiet cup of coffee... for five minutes. Till you hear that "crack" that two heads make when they hit.

What advice would you give Kate about having a second child?

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