Not sure I got exactly right what the claim was, but I took it that it was a) 7 London winners from 2001-2012 had high #'s, and b) these 7 winners won a total of 34 majors. Currently, the math is off 2 majors>maybe I missed some.
Majors start 2006:
Some of these runners won before 2001, like Catherine Ndereba and Khalid Khannouchi (3x Chicago in 1997, 1998, 2000, prior to the sample).
We take the winners of London 2001-2012 (12 years, 24 winners), and try to get 34 major wins from 7 London winners. That’s an average of almost 5! To get that you absolutely need Radcliffe, because there are very few with even 5 major wins, and you need Martin Lel and Khalid Khannouchi with 5 each, and you need Wilson Kipsang, Margaret Okayo, and Irina Mikitenko with 4 each, but that’s six athletes and only 29 majors, so you can’t get to 34 with 7 athletes—you can add one of Rutto, Limo, El Mouaziz (the most likely, Moroccan), Wanjiru, Kebede, and Keitany to get 32, as they have three each. Either I’m missing some major winners or got some numbers off, or they mixed up Priscah and Rita Jeptoo, or maybe they added in World or Olympic titles.
Radcliffe, 7 majors
Lel, Khannouchi 5 majors
Kipsang, Okayo, Mikitenko, 4 majors
Rutto, Limo, El Mouaziz, Wanjiru, Kebede, Keitany, 3 majors
Kipchoge, Kastor, Priscah Jeptoo, Edna Kiplagat, 2 majors
Abera, Emmanuel Mutai, Mergia, Chunxiu, Tufa, 1 major
London
2001 Abdelkader El Mouaziz (3 majors: London 2001, NYC 2000, London 1999) Morocco 2:07:09 Second victory
2002 Khalid Khannouchi (5 majors: London 2002, Chicago 2002, plus Chicago 1997,1999,2000) United States 2:05:38 World marathon record
2003 Gezahegne Abera (1 total) Ethiopia 2:07:56
2004 Evans Rutto (3 majors) Kenya 2:06:18
2005 Martin Lel (5 majors) Kenya 2:07:35
2006 Felix Limo (3 majors) Kenya 2:06:39
2007 Martin Lel Kenya 2:07:41 Second victory
2008 Martin Lel Kenya 2:05:15 Course record; third victory
2009 Samuel Wanjiru (3 majors) Kenya 2:05:10 Course record
2010 Tsegaye Kebede (3 majors) Ethiopia 2:05:19 Provisional Result
2011 Emmanuel Mutai (1 major) Kenya 2:04:40 Course record
2012 Wilson Kipsang (4 majors) Kenya 2:04:44
2013 Tsegaye Kebede Ethiopia 2:06:04 Second victory
2014 Wilson Kipsang Kenya 2:04:29 Course record; second victory
2015 Eliud Kipchoge (2 majors) Kenya 2:04:42
2001 Derartu Tulu Ethiopia (2 majors in this time frame, maybe total) 2:23:57
2002 Paula Radcliffe (7 majors) United Kingdom 2:18:56 Course record
2003 Paula Radcliffe United Kingdom 2:15:25 World marathon record; second victory
2004 Margaret Okayo (4 majors) Kenya 2:22:35
2005 Paula Radcliffe United Kingdom 2:17:42 Third victory
2006 Deena Kastor (2 majors) United States 2:19:35
2007 Zhou Chunxiu (1 major) China 2:20:38
2008 Irina Mikitenko (4 majors) Germany 2:24:14
2009 Irina Mikitenko Germany 2:22:11 Second victory
2010 Aselefech Mergia (1 major) Ethiopia 2:22:38 Initially third but Liliya Shobukhova and Inga Abitova both disqualified retrospectively.
2011 Mary Keitany (3 majors) Kenya 2:19:19
2012 Mary Keitany Kenya 2:18:37 Second victory
2013 Priscah Jeptoo (2 majors) Kenya 2:20:15
2014 Edna Kiplagat (2 majors) Kenya 2:20:21
2015 Tigist Tufa (1 major) Ethiopia 2:23:21
Boston
2001 Lee Bong-Ju South Korea 2:09:43
2002 Rodgers Rop Kenya 2:09:02
2003 Robert Kipkoech Cheruiyot Kenya 2:10:11
2004 Timothy Cherigat Kenya 2:10:37
2005 Hailu Negussie Ethiopia 2:11:44
2006 Robert Kipkoech Cheruiyot Kenya 2:07:14 2nd victory, course record
2007 Robert Kipkoech Cheruiyot Kenya 2:14:13 3rd victory
2008 Robert Kipkoech Cheruiyot Kenya 2:07:45 4th victory
2009 Deriba Merga Ethiopia 2:08:42
2010 Robert Kiprono Cheruiyot Kenya 2:05:52 course record
2011 Geoffrey Mutai Kenya 2:03:02 course record, fastest marathon ever up to that point
2012 Wesley Korir Kenya 2:12:40
2013 Lelisa Desisa Benti Ethiopia 2:10:22
2014 Meb Keflezighi United States (CA) 2:08:37 First American win since 1983
2015 Lelisa Desisa Benti Ethiopia 2:09:17
2001 Catherine Ndereba Kenya 2:23:53 2nd victory
2002 Margaret Okayo Kenya 2:20:43 course record
2003 Svetlana Zakharova Russia 2:25:19
2004 Catherine Ndereba Kenya 2:24:27 3rd victory
2005 Catherine Ndereba Kenya 2:25:12 4th victory
2006 Rita Jeptoo (4 majors+1)Kenya 2:23:38
2007 Lidiya Grigoryeva Russia 2:29:18
2008 Dire Tune Ethiopia 2:25:25
2009 Salina Kosgei Kenya 2:32:16
2010 Teyba Erkesso Ethiopia 2:26:11
2011 Caroline Kilel Kenya 2:22:36
2012 Sharon Cherop Kenya 2:31:50
2013 Rita Jeptoo Kenya 2:26:25 2nd victory
2014 Rita Jeptoo Kenya 2:18:57 3rd victory, course record
2015 Caroline Rotich Kenya 2:24:55
New York
2001 Tesfaye Jifar Ethiopia Ethiopia 2:07:43 Course record
2002 Rodgers Rop Kenya Kenya 2:08:07
2003 Martin Lel Kenya Kenya 2:10:30
2004 Hendrick Ramaala South Africa South Africa 2:09:28
2005 Paul Tergat Kenya Kenya 2:09:30
2006 Marílson Gomes dos Santos Brazil Brazil 2:09:58
2007 Martin Lel Kenya Kenya 2:09:04 2nd victory
2008 Marílson Gomes dos Santos Brazil Brazil 2:08:43 2nd victory
2009 Meb Keflezighi United States USA 2:09:15
2010 Gebregziabher Gebremariam Ethiopia Ethiopia 2:08:14
2011 Geoffrey Mutai Kenya Kenya 2:05:06 Course record
2012 Cancelled due to Hurricane Sandy
2013 Geoffrey Mutai Kenya Kenya 2:08:24 2nd victory
2014 Wilson Kipsang Kenya Kenya 2:10:59
2001 Margaret Okayo Kenya Kenya 2:24:21 Course record
2002 Joyce Chepchumba Kenya Kenya 2:25:56
2003 Margaret Okayo Kenya Kenya 2:22:31 Course record, 2nd victory
2004 Paula Radcliffe United Kingdom United Kingdom 2:23:10
2005 Jeļena Prokopčuka Latvia Latvia 2:24:41
2006 Jeļena Prokopčuka Latvia Latvia 2:25:05 2nd victory
2007 Paula Radcliffe United Kingdom United Kingdom 2:23:09 2nd victory
2008 Paula Radcliffe United Kingdom United Kingdom 2:23:56 3rd victory
2009 Derartu Tulu Ethiopia Ethiopia 2:28:52
2010 Edna Kiplagat Kenya Kenya 2:28:20
2011 Firehiwot Dado Ethiopia Ethiopia 2:23:15
2012 Cancelled due to Hurricane Sandy
2013 Priscah Jeptoo Kenya Kenya 2:25:07
2014 Mary Keitany Kenya Kenya 2:25:07
Chicago
October 7, 2001 Ben Kimondiu Kenya 2:08:52
Catherine Ndereba Kenya 2:18:47^
October 13, 2002 Khalid Khannouchi United States 2:05:56
Paula Radcliffe United Kingdom 2:17:18^
October 12, 2003 Evans Rutto Kenya 2:05:50
Svetlana Zakharova Russia 2:23:07
October 10, 2004 Evans Rutto Kenya 2:06:16
Constantina Diţă-Tomescu Romania 2:23:45
October 9, 2005 Felix Limo Kenya 2:07:02
Deena Kastor United States 2:21:25
October 22, 2006 Robert Kipkoech Cheruiyot Kenya 2:07:35
Berhane Adere Ethiopia 2:20:42
October 7, 2007 Patrick Ivuti Kenya 2:11:11
Berhane Adere Ethiopia 2:33:49
October 12, 2008 Evans Cheruiyot Kenya 2:06:25
Lidiya Grigoryeva Russia 2:27:17
October 11, 2009 Samuel Wanjiru Kenya 2:05:41
Irina Mikitenko Germany 2:26:31
October 10, 2010 Samuel Wanjiru Kenya 2:06:23
Atsede Baysa Ethiopia 2:23:40
October 9, 2011 Moses Mosop Kenya 2:05:37
Ejegayehu Dibaba Ethiopia 2:22:09
October 7, 2012 Tsegaye Kebede Ethiopia 2:04:38
Atsede Baysa Ethiopia 2:22:03
October 13, 2013 Dennis Kimetto Kenya 2:03:45
Rita Jeptoo Kenya 2:19:57
October 12, 2014 Eliud Kipchoge Kenya 2:04:11
Mare Dibaba Ethiopia 2:25:37
Berlin
2014 Dennis Kimetto Kenya 2:02:57 WR Tirfi Tsegaye Ethiopia 2:20:18
2013 Wilson Kipsang Kiprotich Kenya 2:03:23 WR Florence Kiplagat Kenya 2:21:13
2012 Geoffrey Mutai Kenya 2:04:15 Aberu Kebede Ethiopia 2:20:30
2011 Patrick Makau Musyoki Kenya 2:03:38 WR Florence Kiplagat Kenya 2:19:44
2010 Patrick Makau Musyoki Kenya 2:05:08 Aberu Kebede Ethiopia 2:23:58
2009 Haile Gebrselassie Ethiopia 2:06:08 Atsede Habtamu Besuye Ethiopia 2:24:46
2008 Haile Gebrselassie Ethiopia 2:03:59 WR Irina Mikitenko Germany 2:19:19
2007 Haile Gebrselassie Ethiopia 2:04:26 WR Gete Wami Ethiopia 2:23:17
2006 Haile Gebrselassie Ethiopia 2:05:56 Gete Wami Ethiopia 2:21:34
2005 Philip Manyim Kenya 2:07:41 Mizuki Noguchi Japan 2:19:12
2004 Felix Limo Kenya 2:06:44 Yoko Shibui Japan 2:19:41
2003 Paul Tergat Kenya 2:04:55 WR Yasuko Hashimoto Japan 2:26:32
2002 Raymond Kipkoech Kenya 2:06:47 Naoko Takahashi Japan 2:21:49
2001 Joseph Ngolepus Kenya 2:08:47 Naoko Takahashi Japan 2:19:46 WR
Tokyo 2013-
2015 Endeshaw Negesse Ethiopia 2:06:00 Birhane Dibaba Ethiopia 2:23:15
2014 Dickson Chumba Kenya 2:05:42 Tirfi Tsegaye Ethiopia 2:22:23
2013 Dennis Kimetto (3 majors) Kenya 2:06:50 Aberu Kebede Ethiopia 2:25:34