 Operation Tracer was a top @-@ secret British stay @-@ behind spying mission that was only to be implemented if Gibraltar was captured by the Axis Powers . Six men were to be sealed in a cave and left with only enough supplies for a year . The volunteers — two doctors , three signalmen and their leader — would run an observation post with one 12 @-@ inch ( 300 mm ) by 6 @-@ inch ( 150 mm ) slit looking over the harbour and a concealed outdoor terrace over the Mediterranean . The team would then wire back all shipping movements to the British Admiralty . 
 Operation Tracer was a top @-@ secret British stay @-@ behind spying mission that was only to be implemented if Gibraltar was captured by the Axis Powers . Six men <a href='uninflect' title='1'><mark>were</mark></a> to be sealed in a cave and left with only enough supplies for a year . The volunteers <a href='uninflect' title='2'><mark>—</mark></a> two doctors , three signalmen and their leader — would run an observation post with one 12 @-@ inch ( 300 mm ) by 6 @-@ inch ( 150 mm ) slit looking over the harbour and a concealed outdoor terrace over the Mediterranean . The team would then wire back all shipping movements to the British Admiralty . 
Operation Tracer was a top @-@ secret British stay @-@ behind spying mission dat was only to be implemented if Gibraltar was captured by the Axis Powers . Six men was to b sealed in a cave and left w only enough supplies for a year . The volunteers ——ed two doctors , three signalmen and their leader — would run an observation post witw/e 12 @-@ inch ( 300 mm ) by 6 @-@ inch ( 150 mm ) slit looking ova da harbour and a concealed outdoor terrace oovathe Mediterranean . Tdateam would then wire bk all shipping movements to thdaritish Admiralty .