On the day they learned they were being moved to a flat of less than 30 square metres, Yeung Liu-Chun told us she and her husband could not sleep the whole night. Why? Because it was twice the size of their current apartment, which, in turn, was nearly three times the size of the place they had before.

A family of four in five square metres? Imagine lying flat on the floor with your arms outstretched. You are practically touching the four walls of your living space: a partitioned box with a curtain for a door, in an unbearably hot subdivided apartment that you share with half a dozen other families, with a communal toilet and kitchen.

They made it work, Yeung told us, because when they went to bed their son slept on the floor while their daughter was still small enough to fit in a cot suspended from the ceiling.

To Hong Kong's lasting shame, with all of its gleaming office towers and chauffeur-driven limousines, cubicle-dwelling is the reality for thousands of families like the Yeungs.

Most communities around the world have one particular rare commodity that helps define them and the main object of desire: getting access to clean water sufficient affordable petrol to make a second car possible or enough bandwidth for a good internet connection. In Hong Kong, that object is space. During any conversation in this compact megalopolis, it is only minutes before the subject turns to how much of it you have, what you pay for it and how you make it work.

For most, small rented apartments of one or two bedrooms are the norm, while you scrimp and dream of getting enough together for a mortgage. With escalating property prices, government measures to cool the market now mean families have to find as much as 40 or even 50 per cent of the purchase price to pay as a down payment.

Living in their 13 square metres, for which they pay $500 per month (about half their monthly income), the Yeungs have no way out of rentals. "No matter how hard I work," Yeung told us tearfully, "We will never escape from this." But the public flat they move into next month, with twice as much space for half their current rent - with a rental rate being subsidised by the government - at least offers hope.

Calls to reduce the wealth gap with bigger government give rise to the usual debate about "killing the goose" or "betraying the free market that made Hong Kong great". But when you see the Yeungs' toaster suspended from a string on the wall because there isn't a flat space to put it on, it is difficult to listen to such arguments from someone wearing a string of pearls.

For the record, I should add that after spending 20 years in this fabulous city that we Hong Kongers love and hate, my wife, two children and I live in an apartment with three bedrooms. A room for each child? In Hong Kong? We have arrived!

Returning to our family's relative luxury after visiting the Yeungs, I switch on the TV and catch the end of one of those "Move That Bus!" reality moments after the destruction of a perfectly good palace, which will be replaced by another even bigger one measuring several hundred square metres. Then I smile. Mrs Yeung has already cried tonight, so I just smile.