I agree with AlBags answer. The BS5713-91 serves only to give the specification for a hermetically sealed flat double glazing unit, and does not refer to toughened glass, so doesn't directly affect safety standards.
In a domestic glazed door, any glazing, whether single or double, below 1500mm from the bottom of the door must be of toughened glass,which will be recognized by the British Standard Kite Mark in a corner of the glazed unit.
I believe that before this safety standard was brought in, there were some particularly nasty accidents involving people falling down stairs and smashing into glazed doors, resulting in some horrific accidents due to the jagged shards of glass caused when normal float glass is broken.