Thankyou for this , it shows no cable equivalent size for 50mm metric? Was there not a cable made between these sizes at the time? Which would make sense as the next size up at 64mm would be definitely too large for what I’m seeing on site.This table gives single phase ratings but you may have to take it with a pinch of salt.
Comparison of imperial & metric conductor sizes
The table in this article show the comparison of imperial and metric conductor sizes in detailwww.daenotes.com