This is the only information which we have, from his name on the original Memorial Plaque in St Werburgh's. There are several possibilities for regiments, but no details of these men give a link to Chester or St Werburgh's.
There is one possible family of which John may be a member. Edward and Catherine Carroll came to live at Castle Street in Chester, from Mold, some time before 1891. They ran a lodging house here. Most of their children, including John age 16 had been born in Mold, whilst other younger ones had been born in Chester and baptised at either St Francis' or St Werburgh's. This seems a possible family for the John Carroll listed.
John's service record has not survived and his name is not recorded by the Commonwealth War Graves Commission.