From:
This Prisoner of War record for J J Mare was transcribed record from various documents held at the National Archives, South Africa, including arrest and shipping information from newspaper sources like De Zuid-Afrikaan.
https://www.gendatabase.com/boer-war-prisoner-record.php?q=9704&r=J J&s=Mare&ref=
This set of Prisoner of War documents can be accessed online via the FamilySearch.org project by Clicking Here.