A dispersionless integrable system associated to Diff$(S^1)$ gauge   theory
  A dispersionless integrable system underlying 2+1-dimensional hyperCR Einstein--Weyl structures is obtained as a symmetry reduction of the anti--self--dual Yang--Mills equations with the gauge group Diff$(S^1)$. Two special classes of solutions are obtained from well known soliton equations by embedding SU(1,1) in ${Diff}(S^1)$. 
Maciej Dunajski, George Sparling