My wife has a Visitor Visa for Canada and daughter has Study Permit for Canada which is valid more than six months from the date they are travelling.
They have a layover at London for 6 hours which does not cross the day meaning day of landing and boarding the next flight is on the same day.
So, do they require a Transit Visa? I have already gone through the tool to check the same but I could not understand last question which says ask your airline whether you need to pass the border control.