Delphi append to (memo1) text file

Hi Experts,
Delphi app using an Access db.
Trying to archive deleted records to a text file before deletion.
(I'm testing this from a form button currently, but would integrate it in to the delete records procedure when working, so that it saves text file before deleting.)
Writing a new file (SaveToFile) is no problem - but trying to append to it is!
rtwoolf gave me this code some weeks ago for another area where only new (overwritten) files are required.
I added in the code under '//new section' at the bottom to try and write if not existing, or append if existing.
The 'SaveToFile' line works fine - but the 'Append' line seems to do nothing - text file remains as before! (even if I comment out the other code leaving it as the only option)
Ideally, I would like to add a date/time stamp at the append point too if that's possible.
***********
procedure TFrameDeleteConts.DeletedTextBtnClick(Sender: TObject);
    var
    ds : TDataSet;
    i : integer;
    linebuffer : string;
  begin
    // Produce text file ...........
    ds := DBGrid1.DataSource.DataSet;
    //insert fields header into memo
    linebuffer := '';
  for i := 0 to ds.fieldcount - 1 do
  begin
    linebuffer := linebuffer + '"' + ds.FieldList[i].FieldName + '"';
  if i < ds.fieldcount - 1 then linebuffer := linebuffer + ',';
  end;
     // Clear Test*******
    memo1.clear;
    memo1.Lines.append(linebuffer);
  //insert all records
    ds.first;
  while ds.Eof = false do
  begin
    //insert all records into memo
    linebuffer := '';
  for i  := 0 to ds.fieldcount - 1 do
  begin
    linebuffer := linebuffer + '"' +  ds.fieldlist[i].AsString + '"';
    if i < ds.fieldcount - 1 then linebuffer := linebuffer + ',';
  end;
    memo1.Lines.append(linebuffer);
    ds.next;
    end;
    //New section
   if SysUtils.FileExists('C:\No25Data\Text\No25Deleted.txt')=true
   then
   // This is the problem line
   Memo1.lines.Append('C:\No25Data\Text\No25Deleted.txt')
   else
   Memo1.lines.SaveToFile('C:\No25data\Text\No25Deleted.txt');
    end;

I'm a beginner with Delphi.
Have tried TextFile routines with AssignFile (then Rewrite and Append) but they didn't work either.
Thanks.