When I asked her what she wanted to teach the new arrival the other week, D looked at me and replied, ever so sweetly:
'How to be a lady.'
My heart melted with delight. Of course, D's definition of being a 'lady' is loose – she loves to giggle as she grabs onto people's bottoms, has a penchant for drinking her milk using the classy technique of dipping her hand into the cup and then loudly sucking her fingers and her culinary efforts of late include dipping everything from pasta to salmon into her glass of water before eating – but D seems genuinely excited about imparting all of her knowledge to her little sister.
Let's hope this lasts. Even if it means I have another handbag-obsessed, shoe-crazed, jewellery-thieving child on my hands within a matter of months.
Although, if it involves D teaching new babe her latest technique of getting out of the naughty corner - strut out of it within seconds of being put there, brush my cheek with her hand and whisper in my ear: 'I missed you SO much' before resuming her playing/eating/running around, which left me so taken aback that I could only stare at D in awe - I am in serious trouble.
I am feeling very conscious that these last several weeks before I give birth are especially precious because all of the special moments that I have with Diana now - the baths where we draw hearts on each other in coloured crayons, our multiple story sessions, cuddling up under the covers together - will still exist, but differently. And with another person involved.
To ease the transition, we've been reading lots of books about new arrivals and second babies, taking D's baby dolls in the baby buggy everywhere with us, going to midwife appointments together and spending some time with friends' newborns, so Diana gets some exposure to very young infants (She absolutely adores them. Hopefully that will translate even when one is taking time and attention away from her).
And we've been chatting, lots, about how D will be a big sister and will be able to help out with the baby, whether that involves giving her a cuddle or singing her a song. D seems most interested in teaching her sibling about Bolshy the bulldog, who used to boss her about as an infant but now spends his days being happily bullied by his younger sister.
Which got me thinking: I've been fretting about how my daughter will respond to the new arrival, but what about the real lord of the house? How is Bolshy going to cope with another baby who will soon be pulling his ears and screaming his name?
And, more crucially, how am I going to kick this kid out of my bed – which he's adopted as his own in recent months – to make room for baby number two?