Oh yes they definitely knew this was coming, but as ever they try to delay the inevitable for as long as possible so that hopefully it's someone else's problem when it does come to the surface.
It's going to be painful for those that bought at the top with a short two year fix. But that is a very small number of people. Pain for anyone obviously isn't good, but house prices out of control cause so much damage throughout the entire country.
They did stress test with a base rate +3%. So many have been stress tested up to 5%. But really they should have stress tested the long-term average rates of 6% + 3%. The BoE is certainly not the white knight it's often portrayed as. There's an awful lot they've done wrong.
Mortgage holders that bought ages ago and have had many years on artificially low rates should be thankful for that rather than complaining that rates are now going back to the norm. I bet their mortgages now are still a hell of a lot lower than my rent.