Common method that offenders are, once again, using to break into residential properties.
This often involves them gaining entry from the rear of a house via UPVC French Doors by snapping out the lock barrel in the outer handles.
The below link shows a simple device in the form of a tube that slides over the internal handles of French Doors and prevents the handles being turned from the outside even if the outside lock is snapped.
There are a number of similar devices available on line that you may wish to consider.
They have a starting price of around £25.00.
https://members.neighbourhoodlink.co.uk/AlertMessage/Attachment/6A68C7C3B86475B8C6EADEA07D8F41D4