Thank you all who have replied

Thank you,

I also asked D.T.Brown who referred me to a BBC Gardeners World Magazine article:

The response was:

Dry off the cut tuber.

Lightly dust the surface with wood ash to prevent rotting.

Thank you KG Magazine

My seed potatoes vary greatly in size from 24 per bag to 14 per bag..

Memory is that my father many years ago would cut large seed potatoes vertically.

Is this practice still done and do I need to protect the cut surface and how?