Exhibit
10.53

    


    EXECUTION
VERSION

    


    December
12, 2009

    


    Highbury
Financial Inc.

    999
Eighteenth Street

    Suite
300

    Denver,
Colorado  80202

    Attention:  R.
Bradley Forth

    


    Mr.
Forth:

    


    Reference
is hereby made to that certain Agreement and Plan of Merger, dated as of
December 12, 2009 (the “Merger Agreement”), by and among Highbury Financial
Inc., a Delaware corporation (the “Company”), Affiliated Managers Group, Inc., a
Delaware corporation, and Manor LLC, a Delaware limited liability
company.  Capitalized terms used but not otherwise defined herein
shall have the meanings set forth in the Merger Agreement.

    


    The
undersigned hereby agree that immediately prior to the consummation of the
Merger and without any further notice from the Company, each of the undersigned
shall exchange each share of Series B Preferred Stock of the Company held by the
undersigned, including all accrued and unpaid dividends on such share, into, and
the Company shall issue to the undersigned, that number of fully paid and
nonassesable shares of Company Common Stock as is equal to the Conversion Number
(as such term is defined in the Certificate of Designation of Series B
Convertible Preferred Stock of Highbury Financial Inc., filed with the Secretary
of State of the State of Delaware on August 10, 2009 (the “Series B Certificate
of Designation”)).

    


    The
undersigned hereby agree that the exchange of the Series B Preferred Stock for
Company Common Stock is intended to constitute a "recapitalization" within the
meaning of Section 368(a)(1)(E) of the Internal Revenue Code of 1986, as amended
(the “Code”).  None of the undersigned shall take any contrary
position on any tax return or in any audit, claim, investigation or proceeding
before any governmental authority, unless required pursuant to a final
determination within the meaning of Section 1313 of the Code.  This
letter agreement shall constitute a "plan of reorganization" within the meaning
of the Treasury Regulations promulgated pursuant to Section 368 of the
Code.  Each of the undersigned shall comply with all reporting and
record-keeping requirements set forth in Treasury Regulation Section 1.368-3,
and Sections 6043(c) and 6043A of the Code, if applicable.  Each of
the undersigned shall provide such information and assistance as is reasonably
requested by another party hereto in order to comply with the reporting and
record-keeping requirements referenced in the immediately preceding
sentence.


    
      
         


      

      
         


        
          

        

      

      
         


      

    


    This
letter agreement shall be governed by and construed in accordance with the laws
of the State of Delaware without regard to the conflicts of law provisions
thereof.  This letter agreement may be executed in any number of
counterparts (including by facsimile), each of which shall be an original and
all of which taken together shall constitute one and the same
instrument.

    


    Please
indicate your agreement to the terms set forth above by executing this letter
agreement where indicated below.

    


    
      
        
          
            
              
                
                  
                    
                      
                        
                          
                            	
                                    HIGHBURY
      FINANCIAL INC.

                                  
	 
      	 
      
	
                                    By:

                                  	
                                      /s/
      Richard S. Foote

                                  
	Name:  
      Richard
      S. Foote
	Title:    
      President
      and Chief Executive Officer
	 
      	 
      
	
                                    SDB
      Aston, Inc.

                                  
	 
      	 
      
	
                                    By:

                                  	
                                     
      /s/ Stuart D. Bilton

                                  
	Name:  
      Stuart
      D. Bilton
	Title:    
      President
	 
      	 
      
	
                                    KCA
      Aston, Inc.

                                  
	 
      	 
      
	
                                    By:

                                  	
                                     
      /s/ Kenneth Anderson

                                  
	Name:  
      Kenneth
      Anderson
	Title:    
      President
	 
      	 
      
	
                                    GFD
      Aston, Inc.

                                  
	 
      	 
      
	
                                    By:

                                  	
                                     
      /s/ Gerald Dillenburg

                                  
	Name:  
      Gerald
      Dillenburg
	Title:    
      President
	 
      	 
      
	
                                    CRD
      Aston, Inc.

                                  
	 
      	 
      
	
                                    By:

                                  	
                                     
      /s/ Christine Dragon

                                  
	Name:  
      Christine
      Dragon
	Title:    
      President


                          

                        

                      

                    

                  

                

              

            

          

        

      

    


    
      
         


      

      
         


        
          

        

      

      
         


      

    

    


    
      
        
          
            
              
                
                  
                    
                      
                        	
                                JH
      Aston, Inc.

                              
	 
      	 
      
	
                                By:

                              	
                                 
      /s/ Joseph Hays

                              
	Name: 
       Joseph
      Hays
	Title:    
      President
	 
      	 
      
	
                                BCH
      Aston, Inc.

                              
	 
      	 
      
	
                                By:

                              	
                                 
      /s/ Betsy C. Heaberg

                              
	Name:  
      Betsy
      C. Heaberg
	Title:    
      President
	 
      	 
      
	
                                DAR
      Aston, Inc.

                              
	 
      	 
      
	
                                By:

                              	
                                 
      /s/ David Robinow

                              
	Name:  
      David
      Robinow
	Title:    
      President
	 
      	 
      
	
                                JPR
      Aston, Inc.

                              
	 
      	 
      
	
                                By:

                              	
                                 
      /s/ John P. Rouse

                              
	Name:  
      John
      P. Rouse
	Title:    
      President