This photograph is captioned:
Lady Watson, the Mayor, and Col. Storrs at the Y.W.C.A. Fete, Nov. 11th. First Armistice anniversary, 1919
But who is the man standing at the right?
I think it is J.L. Magnes. See here and especially this one:
Part of Magnes' success in political life - Brit Shalom, etc. - was do to family connections, as for example his wife::
In 1907, Beatrice met Judah L. Magnes on a camping trip in the Adirondacks hosted by Louis Marshall (who married Beatrice's sister Florence). Magnes had just returned from a trip to a Zionist Congress in Palestine. During the same year, Beatrice attended the first meeting of the Hadassah Study Circle, a group of women, including Henrietta Szold, that met to discuss Jewish history and Zionism, topics in which Beatrice was becoming increasingly interested. Beatrice married Judah L. Magnes in 1908.
In that Jerusalem fete picture, he is at a political center with central political people.
And as for Magnes:
...in 1928, Magnes, who was initially responsible only for the university's finances and administrative staff, had his authority extended to academic and professional matters, Einstein resigned from the Board of Governors. Einstein wrote:
The bad thing about the business was that the good Felix Warburg, thanks to his financial authority ensured that the incapable Magnes was made director of the Institute, a failed American rabbi, who, through his dilettantish enterprises had become uncomfortable to his family in America, who very much hoped to dispatch him honorably to some exotic place. This ambitious and weak person surrounded himself with other morally inferior men, who did not allow any decent person to succeed there ... These people managed to poison the atmosphere there totally and to keep the level of the institution low.