Sparklefizz Not many people have said they never lock their doors, and few have said they leave their doors unlocked when they leave the house. Few leave their front doors unlocked Mostly it is a question of whether you leave back doors unlocked when in the house or garden.
Having had three magnificent sets of French doors installed last year, they have been open most of the time this summer, but we have a secure back garden and always lock them if we leave the house.
Your insurance is only invalid if you leave the house empty when doors are unlocked. If you are on the premises or in the garden your insurance is valid, whether the back doors are open or shut and locked.