Glimpsed in the Eurostar Terminal

While I'm trying to work out what the poster is trying to say about Us, (is London really famous for Wierd Hair and Whacky Glasses?) I'm distracted by a family arriving for 'Enregistrement'.
The couple, from the middle east, are arguing with each other in arabic. The man is waving tickets in the air. The father has close cropped hair, a broad, dark face and is significantly overweight. The two heavy, gold rings on the fingers of his left hand sink into his flesh.
The woman is in her thirties, unsmiling, and appears to be overwhelmed by the two small boys - a hyperactive toddler of about three and a shrieking baby.
With them is a young black girl, slim and pretty, who looks hardly more than sixteen. She is already wheeling a double buggy larger than herself, but the woman dumps the squirming baby in her arms and walks off towards the shopping mall. The little boy, tugging at the girl’s jacket is screaming ‘I want chocolate. Get me chocolate!’ He turns and runs down the concourse after his mother. The girl abandons the buggy and runs after him, clutching the baby. When she returns, dragging the toddler behind her, she looks exhausted. The parents walk slowly back, still arguing. I hope they pay her well, but I doubt if she’s enjoying the job.
I was a nanny once, for a couple of months. Desperate to get to London as a teenager, I answered an advert in the Lady for a mother’s help. My employers lived in Kensington and, although they paid super-tax, they weren’t rich enough to employ the Norland Nanny they coveted. So they had a series of girls like me (I was number four), and they dressed us in uniform as pretend nannies. I was barely eighteen, with no experience of children at all, but I found myself in sole charge of a one year old girl. She was delightful, but I had no aptitude for domestic drudgery. One day off a week and one evening (with a curfew) were no use to a dreamy girl from a hill farm in the north of England, desperate to taste the delights of the Big City! I got the sack when a boy I knew thoughtlessly rang the house telephone to talk to me at two in the morning and my employer - charging into my bedroom to shout at me - discovered I still hadn’t come home from the party I’d gone out to! Being sacked was mortifying, but also a great relief. I found a bedsit and a proper job and began to enjoy my new independence. I often wonder what happened to the little girl and how many unsuitable nannies she had to endure before she grew up.