Problem with the Mansion Tax is that in the London Area quite a modest terraced house or even a large flat could count as a 'Mansion', whereas up North even a genuine mansion might not. Apart from anything else, people who own historic mansions have had a hard enough time looking after them without this additional tax, which might bear no resemblance to their actual incomes. Crazy proposal, as you might expect from the Labour Party! 
P.S. I do not own a mansion or anything like it.
P.S. I do not own a mansion or anything like it.