There are areas of London where large numbers of flats and houses are unoccupied. People buy them solely for investment:
Observer 2015
"Racine [a restaurant owner who has had to sell up] is the latest victim of what some have called “lights-out London” where absentee owners push up property prices without contributing to the local economy. When Racine opened in 2002 the average price of a Knightsbridge home was £745,000; now it is £3.4m. There are an estimated 22,000 empty properties in London, partly a consequence of the city’s status as what the novelist William Gibson has called “the natural home of a sometimes slightly dodgy flight capital”. "
This has encouraged developers to build more and more of these properties, with ever-increasing prices, which has a knock-on effect for everybody else. Many people who would previously have been thought of as very well off can no longer afford to buy, or rent, in inner London. They are moving out to what were formerly affordable areas for people on average salaries - and so pushing up prices there too. So the housing market is being artificially over-heated everywhere, but particularly in the south east.
This was reported in the Guardian in 2016:
"Tens of thousands of London homes have been left uninhabited for so long they are considered “long-term vacant” with more than 1,100 of them empty for over a decade, according to data obtained by the Guardian.
"Despite a chronic shortage of housing in the capital, more than 22,000 homes have been left empty by their owners for longer than six months, data received from London boroughs in response to freedom of information requests has revealed.
"Councils looking to bring vacant properties back into use have a range of options, including levying an additional rate of council tax, helping homeowners with the cost of repairs, or even compulsory purchase orders.
"Since April 2013 councils have been able to impose a punitive “empty homes premium” of an additional 50% council tax, disincentivising homeowners from admitting that they are leaving properties empty.
"... some councils are beginning to take action against the phenomenon of “buy to leave”, whereby asset speculators buy homes with the intention of leaving them uninhabited so as to take maximum advantage of spiralling London property prices.
And this Guardian article, also from 2016:
"Freedom of information requests by Inside Housing show that of the £1bn raised since 2012 to replace right to buy, £27.3m of it has been used to buy back homes sold under right to buy.
"The government encourages the sale of council houses by offering attractive discounts to tenants, who understandably choose to buy. The council is then faced with dwindling stocks while waiting lists lengthen and homelessness spikes. So it uses its cash to buy back the homes it could not afford to lose in the first place."
So it seems councils have the power to buy properties, and some councils do exactly that. K&C has, as people must have read in the newspapers, £374 million at its disposal. It is the richest council in the country and if poorer councils can do it, then why can't K&C?
I am not going to shed any tears over people who leave their properties unoccupied for years just to inflate their already inflated wealth, at a time while thousands are effectively homeless. And you may ask why so many of these investors choose London. Some commentators have suggested it is because in many other countries it is either not allowed - or made very difficult - for non-residents to purchase property, or there is a significant financial cost to be paid to the government for doing so.