Can a DNO Service Cut-out be used as the primary source of fault current protection, when the DB it supplies is more than 3m from the intake?

From a practical point of view it should be fine, provided that the cables are correctly sized in relation to the fuse.

The DNO may however say otherwise, which is their prerogative. It COULD also be argued that the installation is not compliant with BS 7671, due to the omission of fault protection to conductors longer than 3 m

This in MY VIEW is incorrect, I would argue that the cut out fuse does provide fault protection to a correctly sized downstream cable. This may be confirmed by reference to fuse data and cable ratings. The fact that that the DNO will not confirm this is not in my view relevant, provided that the installer is satisfied. In what way does the ownership of the fuse affect the fault protection offered ?

Does anyone really believe that the cut out fuse [owned by the DNO] wont protect a suitably selected cable, but that a second identical fuse owned by the consumer will protect the cable ?

That said, if I was performing the installation, I would add the second fuse, to "tick a box" not because it does any good.

If an existing installation lacked the second fuse, then this would not worry me, provided that published data showed that the installed cable was properly protected by the fuse used, without concern as to whom owned the fuse. If the fuse carrier was sealed and the fuse size not reliably known, then I would presume the worst case.

From a practical point of view it should be fine, provided that the cables are correctly sized in relation to the fuse.

The DNO may however say otherwise, which is their prerogative. It COULD also be argued that the installation is not compliant with BS 7671, due to the omission of fault protection to conductors longer than 3 m

This in MY VIEW is incorrect, I would argue that the cut out fuse does provide fault protection to a correctly sized downstream cable. This may be confirmed by reference to fuse data and cable ratings. The fact that that the DNO will not confirm this is not in my view relevant, provided that the installer is satisfied. In what way does the ownership of the fuse affect the fault protection offered ?

Does anyone really believe that the cut out fuse [owned by the DNO] wont protect a suitably selected cable, but that a second identical fuse owned by the consumer will protect the cable ?

That said, if I was performing the installation, I would add the second fuse, to "tick a box" not because it does any good.

If an existing installation lacked the second fuse, then this would not worry me, provided that published data showed that the installed cable was properly protected by the fuse used, without concern as to whom owned the fuse. If the fuse carrier was sealed and the fuse size not reliably known, then I would presume the worst case.