I've been asked to look at some old Christmas tree lights.

I am confident this will be the of the direct mains type with single
insulated twisted pair and probably conforming to BS 4647:1970.

I am aware new mains lights of this type would have additional
insulation as per BS EN 60335.

Obviously I can only do a visual inspection on them, but what is the
current thinking of single insulated mains cable in terms of PAT or
equivalent testing?