It's foreign money pouring into the British property market because the cost of investing in British property is so low. It's like a free bank account.
There was a comparison done between a similar sized property in Manhattan and in central London. The US property attracted $14k a year in property taxes; the British property less than £4k pa.
Even the Met Police have said that most of the money pouring into London property from abroad is criminal proceeds, and has grossly inflated the market to the detriment of British citizens
This, then, impacts the rest of the country as people who would have once lived in the capital for most of their adult life then move to other cities and suburbs after selling their London flats, pushing up prices in the regions. Which then displaces the traditional people who would have lived in the regions et al.
The answer to this is in the tax system. More council tax bands and high council tax for properties over £1 million. But look what happened when Miliband ventured the idea of a mansion tax...
There's also the issue of property owned by nebulous entities registered in tax shelters, where no one knows exactly who owns the property in question.
I remember when Osborne became chancellor, and he was horrified at how many London properties were exempt from council tax because they were owned by offshire businesses. He closed that loophole, but more should have been done.
Basically, it's the global rich using British property as cheap bank accounts that has caused the housing crisis. Someone with a will of iron needs to come along and shut the practices down, and weather all the blowback that these entities will throw at Britain in return.