I know the subject of SY cables in fixed power installations pops up a lot but please bear with me.
I know that SY cable does not meet any British or harmonised standards and is 'discouraged' under BS 7671, but can be installed and noted as a departure on the installation certificate.
As it will need to be 'safe' under BS 7671, should SY cable be installed in metallic containment such as steel trunking?