Getting TWebbrowser contents HTML into a string

How do I get  TWebbrowser contents HTML into a string.

I found about 10 examples of code that should do that and they all
compile well but give an acess violation if I try to access the body
property of the TWebbrowser document property at runtime.
I use delphi turbo 2006, windows vista business, IE7

example of failing code:

procedure TForm1.BitBtn1Click(Sender: TObject);
var
  Html : string;
  HtmlDocument: OleVariant;
begin

webbrowser1.navigate('http://www.flickr.com/recent_activity.gne?days=');

   HtmlDocument:= WebBrowser1.OleObject.Document;
   memo1.lines.add(Htmldocument.body); // AV here

   webbrowser1.navigate('http://flickr.com/?clear=1');


end;