heart and soul

the choicest or most essential or most vital part of some idea or experience; "the gist of the prosecutors argument"; "the heart and soul of the Republican Party"; "the nub of the story"

और यह काम पूरी तरह से नियामक का है.

Ajit Singh was the heart and soul of this movement and he was helped by Aga Haider and Syed Hyder Riza.