Mark Carney is not "predicting" that house prices will fall by 30% in the event of a no deal Brexit - the Bank of England did stress tests on a range of situations (which is part of their job) and one of the scenarios was a fall in house prices of up to 30% in a worst case scenario and if the banks would be able to cope should this occur.
Suddenly this is reported (mis-reported) by the press yesterday as a new thing and as a prediction when it's old news and not a prediction.
Nov 2016: www.theguardian.com/business/2016/nov/27/bank-of-england-announce-stress-tests-uk-banks-fpc-fsr
August 2018:
"Banks were ready for house prices crashing by a third, interest rates soaring by more than 4 per cent and the economy going into recession – the worst case scenario."
www.independent.co.uk/news/uk/politics/brexit-no-deal-uk-prices-trade-mark-carney-bank-of-england-warning-a8475531.html
These stress test were also done long before the referendum by the way: April 2014 : www.bbc.co.uk/news/business-27202546
"Bank of England Governor Mark Carney said on Friday the central bank was not predicting big falls in house prices, despite having told banks last year to be prepared for falls of up to a third if there was economic turmoil after Brexit.
British media had reported late on Thursday that Carney had warned senior ministers earlier in the day that a chaotic Brexit could lead to house price falls of up to 35 percent over three years as well as spiraling interest rates.
Carney did not directly address the media reports in a question and answer session after a speech at the Irish central bank, but said bank ‘stress test’ scenarios in which house prices fell sharply did not amount to a prediction from the BoE.
“That’s not a prediction of what’s going to happen, but that’s what we need to do in order to make sure that ... the system is very clearly and transparently ... able to continue to lend,” he said.
www.reuters.com/article/us-britain-boe-houseprices/bank-of-england-not-predicting-big-house-price-fall-carney-idUSKCN1LU1IQ