diff --git a/Grid/qcd/action/pseudofermion/DomainDecomposedBoundaryTwoFlavourPseudoFermion.h b/Grid/qcd/action/pseudofermion/DomainDecomposedBoundaryTwoFlavourPseudoFermion.h
new file mode 100644
index 00000000..a959d889
--- /dev/null
+++ b/Grid/qcd/action/pseudofermion/DomainDecomposedBoundaryTwoFlavourPseudoFermion.h
@@ -0,0 +1,152 @@
+/*************************************************************************************
+
+    Grid physics library, www.github.com/paboyle/Grid 
+
+    Source file: ./lib/qcd/action/pseudofermion/DomainDecomposedTwoFlavourBoundary.h
+
+    Copyright (C) 2021
+
+Author: Peter Boyle <paboyle@ph.ed.ac.uk>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+    See the full license in the file "LICENSE" in the top level distribution directory
+*************************************************************************************/
+/*  END LEGAL */
+#pragma once
+
+NAMESPACE_BEGIN(Grid);
+
+///////////////////////////////////////
+// Two flavour ratio
+///////////////////////////////////////
+template<class Impl>
+class DomainDecomposedBoundaryTwoFlavourPseudoFermion : public Action<typename Impl::GaugeField> {
+public:
+  INHERIT_IMPL_TYPES(Impl);
+
+private:
+  SchurFactoredFermionOperator<Impl> & DenOp;// the basic operator
+
+  OperatorFunction<FermionField> &DerivativeSolver;
+  OperatorFunction<FermionField> &ActionSolver;
+
+  FermionField Phi; // the pseudo fermion field for this trajectory
+
+  RealD refresh_action;
+public:
+  DomainDecomposedBoundaryTwoFlavourPseudoFermion(SchurFactoredFermionOperator<Impl>  &_DenOp,
+				    OperatorFunction<FermionField> & DS,
+				    OperatorFunction<FermionField> & AS
+				    ) : DenOp(_DenOp),
+					DerivativeSolver(DS), ActionSolver(AS),
+					Phi(_DenOp.FermOp.FermionGrid()) {};
+      
+  virtual std::string action_name(){return "DomainDecomposedBoundaryTwoFlavourPseudoFermion";}
+
+ 
+  virtual std::string LogParameters(){
+    std::stringstream sstream;
+    return sstream.str();
+  }  
+  
+  virtual void refresh(const GaugeField &U, GridSerialRNG& sRNG, GridParallelRNG& pRNG)
+  {
+    // P(phi) = e^{- phi^dag Rdag^-1 R^-1 phi}
+    //
+    // DenOp == R
+    //
+    // Take phi = R eta  ; eta = R^-1 Phi
+    //
+    // P(eta) = e^{- eta^dag eta}
+    //
+    // e^{x^2/2 sig^2} => sig^2 = 0.5.
+    // 
+    // So eta should be of width sig = 1/sqrt(2) and must multiply by 0.707....
+    //
+    RealD scale = std::sqrt(0.5);
+
+    DenOp.ImportGauge(U);
+
+    FermionField eta(DenOp.FermOp.FermionGrid());
+
+    gaussian(pRNG,eta);    eta=eta*scale;
+    
+    DenOp.ProjectBoundaryBar(eta);
+    DenOp.R(eta,Phi);
+
+    refresh_action = norm2(eta);
+  };
+
+  //////////////////////////////////////////////////////
+  // S = phi^dag Rdag^-1 R^-1 phi
+  //////////////////////////////////////////////////////
+  virtual RealD S(const GaugeField &U) {
+
+    DenOp.ImportGauge(U);
+
+    FermionField X(DenOp.FermOp.FermionGrid());
+
+    DenOp.RInv(Phi,X);
+
+    RealD action = norm2(X);
+
+    return action;
+  };
+
+  virtual void deriv(const GaugeField &U,GaugeField & dSdU)
+  {
+    DenOp.ImportGauge(U);
+
+    GridBase *fgrid = DenOp.FermOp.FermionGrid();
+    GridBase *ugrid = DenOp.FermOp.GaugeGrid();
+
+    FermionField  X(fgrid);
+    FermionField  Y(fgrid);
+    FermionField  tmp(fgrid);
+
+    GaugeField   force(ugrid);	
+
+    FermionField DiDdb_Phi(fgrid);      // Vector C in my notes
+    FermionField DidRinv_Phi(fgrid);    // Vector D in my notes
+    FermionField DdbdDidRinv_Phi(fgrid);
+    
+    FermionField Rinv_Phi(fgrid);
+    FermionField RinvDagRinv_Phi(fgrid);
+
+    // R^-1 term
+    DenOp.dBoundaryBar(Phi,tmp);
+    DenOp.Dinverse(tmp,DiDdb_Phi);            // Vector C
+    Rinv_Phi = Phi - DiDdb_Phi;
+    DenOp.ProjectBoundaryBar(Rinv_Phi); 
+ 
+    // R^-dagger R^-1 term
+    DenOp.DinverseDag(Rinv_Phi,DidRinv_Phi); // Vector D
+    DenOp.dBoundaryBarDag(DidRinv_Phi,DdbdDidRinv_Phi);
+    RinvDagRinv_Phi = Rinv_Phi - DdbdDidRinv_Phi;
+    DenOp.ProjectBoundaryBar(RinvDagRinv_Phi);
+
+    X = DiDdb_Phi;
+    Y = DidRinv_Phi;
+    DenOp.FermOp.MDeriv(force,Y,X,DaggerNo);    dSdU=force;
+    DenOp.FermOp.MDeriv(force,X,Y,DaggerYes);   dSdU=dSdU+force;
+
+    dSdU *= -1.0;
+
+  };
+};
+
+NAMESPACE_END(Grid);
+