When designing the restraint systems Britax aimed to strike a delicate balance in terms of the forces needed to open a buckle – high enough to deter children from opening it themselves, but not so high that the buckle can’t be opened by someone else in case of a dangerous accident situation. Equally a more complicated lock system is not legally permitted if it could also prevent an adult being able to open the buckle in an emergency.
In terms of harnessing, its recommend that parents find the best balance between tightening the harness so tightly that the child is uncomfortable and tries to escape from it – and tightening it so loosely that it is easy for the child simply to slide out of the harness. The harness should be a tight fit but without tension against the body (two fingers should be able to fit between the harness and the child's chest). If your child unbuckles or slips out of his harness it’s recommend that you stop immediately and re-harness your child.