In the early twentieth century, global circumstances unimaginable to those whose lives had been in entangled with the history of the Friary both before and after its dissolution gave rise to a brief but extraordinary episode in the site's story: in 1917 it became a camp for German prisoners of war (POWs). Why or how the Friary was selected as the location of a POW camp is unclear, and the exact position of the camp structures within the friary precinct is unknown.

Numbers of German POWs held in Britain grew throughout the Great War and by 1916 the Prisoners of War Employment Committee was set up to organise work for enemy combatants (excluding officers). Edward Milligen Beloe (1871–1932) of King's Lynn, solicitor, antiquary and a leading light of the Norfolk & Norwich Archaeological Society, was assigned the post of camp commandant. Beloe had military experience in the 5th Battalion of the Norfolk Regiment, appearing on the Retired List in 1914 and later serving as Captain in the Royal Defence Corps (RDC). The latter was formed in 1916 to defend important strategic locations in the UK, subsequently being used to guard POW camps.

One aspect of these camps was the need to provide POWs with a means of making small purchases, without furnishing them with money that would be useful after escaping. This problem was solved by using POW camp tokens. For camps on British soil, the tokens were typically uniface sixpence, shilling and higher denomination pieces, made from zinc-plated steel to a generic design. They were utilitarian, and worlds apart from the penny tokens created by Beloe for Burnham Norton (Plate 22). His were bi-faced, struck not only in tin but also in bronze, contrary to DORA (Defence of the Realm Act) regulations. They display the cleverly encrypted date of 1917, coded by enlarged capitals in the wording on the token's obverse, and the legend ‘CAPTIVORUM CUSTOS CAPTIVUS’ translating as ‘the prisoners’ guard is himself a prisoner’. It may seem odd that a swastika symbol also appears on the token, but this is an ancient symbol for peace and good fortune, still retaining this meaning in 1917, and not today's connotations. A surviving POW camp plate (Plate 23) also has one of Beloe's encrypted dates, again for 1917, and was made by the Staffordshire firm of Bishop & Stonier.