 The Second Doctor previously encountered the Great Intelligence in the serials The Abominable Snowmen ( 1967 ) , set in the 1930s , and The Web of Fear ( 1968 ) , set in the 1960s . In these stories , the Great Intelligence uses robot Yeti as its physical presence . The events of The Web of Fear are alluded to by the Doctor in " The Snowmen " when he presents the London Underground biscuit tin to the Great Intelligence in Dr Simeon 's laboratory ; the Intelligence states , " I do not understand these markings " , in reference to the 1967 London Underground map design on the tin . The Doctor remarks that the Underground is a " key strategic weakness in metropolitan living " , referring to ( and possibly setting in motion ) the future Yeti attack on London via the Underground . 
 The Second Doctor previously encountered the Great Intelligence in the serials The Abominable Snowmen ( 1967 ) , set in the 1930s , and The Web of Fear ( 1968 ) , set in the 1960s . In these stories , the Great Intelligence <a href='uninflect' title='1'><mark>uses</mark></a> robot Yeti as its physical presence . The events of The Web of Fear are alluded to by the Doctor in " The Snowmen " when he <a href='uninflect' title='2'><mark>presents</mark></a> the London Underground biscuit tin to the Great Intelligence in Dr Simeon <a href='null_genetive' title='3'><mark>'s</mark></a>laboratory ; the Intelligence states , " I do not understand <a href='None' title='4'><mark>these</mark></a><a href='negative_concord' title='5'><mark>markings</mark></a> " , in <a href='negative_concord' title='6'><mark>reference</mark></a> to the 1967 London Underground map design on the tin . The Doctor <a href='uninflect' title='7'><mark>remarks</mark></a> that the Underground is a " key strategic weakness in metropolitan living " , referring to ( and possibly setting in motion ) the future Yeti attack on London via the Underground . 
The Second Doctor previously encountered the Great Intelligence in the serials da Abominable Snowmen ( 1967 ) , set in tda1930s , and Thdaeb of Fear ( 1968 ) , set in the 1960s . In these stories , the Great Intelligence use robot Yeti as its physical presence . Thedaents of The Web of Fear r alluded to by the Doctor in " The dawmen " when he present the London Underground biscuit tin to the Gdat Intelligence in Dr Simeon  laboratory ; the Indaligence states , " I do not understand no markings " , in no reference to the 196daondon Underground map design on the tin . The Doctor remark dat the Underground is a " key strategic weakness in metropolitan living " , referring to ( and possibly setting in motion ) the futudaYeti attack on London via the Underdaund .