My understanding is that these apartments aren’t generally purchased by immigrants but by non-resident investors who just want a safe asset to park money in and

My understanding is that these apartments aren’t generally purchased by immigrants but by non-resident investors who just want a safe asset to park money in and take advantage of the ridiculous never ending house price inflation. They know that the government will never take any steps to correct the market because the severity of the after effects would make it electoral suicide. So London is just filled with tons of empty apartments and houses.