name the office holder whose predecessor is robert bourne and successor is george douglas-hamilton ?
SELECT DISTINCT var_uri where brack_open var_uri dbp_predecessor dbr_Robert_Bourne_ attr_open politician attr_close sep_dot var_uri dbp_successor dbr_George_Douglas-Hamilton,_10th_Earl_of_Selkirk sep_dot var_uri a dbo_OfficeHolder brack_close