There was a property boom last year. There is still one going on this year. There was a loosening of mortgage availability last year. This was largely due to rates falling at higher loan to value (lower deposit) mortgages. It was also due to more buy to let investors coming back to the market seeing value in the market.
Then came along the Mortgage Market Review (MMR). This tightened criteria and started to include commitments that not all lenders took into account before. Now lenders are continuing the squeeze with income multiples being capped at certain amounts. The Express discusses this today.
There will be more announcements on the way as lenders try and help to cool the housing market. The free market.