A sealing structure , comprising: a first body defining a first surface ; a second body defining: (i) a second surface ; (ii) a gland extending into the second body from the second surface and defining a gland opening on the second surface, wherein the gland is free of both a tool entry point and a tool exit point; and (iii) a retention structure projecting partially across the gland to at least partially define the gland opening; a resilient sealing body positioned within the gland, wherein: (i) the retention structure retains the resilient sealing body within the gland; and (ii) the resilient sealing body forms a fluid seal between the first body and the second body when the resilient sealing body is brought into pressing engagement with both the first surface and the gland, characterised in that said sealing structure further comprises a seal detection structure configured to detect the fluid seal between the first surface and the second surface , wherein the seal detection structure includes at least a first electrically conductive surface , which is defined on the first body , and a second electrically conductive surface , which is defined on the second body , wherein the resilient sealing body is an electrically conductive resilient sealing body , and further wherein the seal detection structure is configured to detect electrical contact between the first electrically conductive surface and the second electrically conductive surface via the electrically conductive resilient sealing body. a first body defining a first surface ; a second body defining: (i) a second surface ; (ii) a gland extending into the second body from the second surface and defining a gland opening on the second surface, wherein the gland is free of both a tool entry point and a tool exit point; and (iii) a retention structure projecting partially across the gland to at least partially define the gland opening; (i) a second surface ; (ii) a gland extending into the second body from the second surface and defining a gland opening on the second surface, wherein the gland is free of both a tool entry point and a tool exit point; and (iii) a retention structure projecting partially across the gland to at least partially define the gland opening; a resilient sealing body positioned within the gland, wherein: (i) the retention structure retains the resilient sealing body within the gland; and (ii) the resilient sealing body forms a fluid seal between the first body and the second body when the resilient sealing body is brought into pressing engagement with both the first surface and the gland, characterised in that said sealing structure further comprises (i) the retention structure retains the resilient sealing body within the gland; and (ii) the resilient sealing body forms a fluid seal between the first body and the second body when the resilient sealing body is brought into pressing engagement with both the first surface and the gland, characterised in that said sealing structure further comprises a seal detection structure configured to detect the fluid seal between the first surface and the second surface , wherein the seal detection structure includes at least a first electrically conductive surface , which is defined on the first body , and a second electrically conductive surface , which is defined on the second body , wherein the resilient sealing body is an electrically conductive resilient sealing body , and further wherein the seal detection structure is configured to detect electrical contact between the first electrically conductive surface and the second electrically conductive surface via the electrically conductive resilient sealing body. <EOS>