// Set path to the iframe file
var filePath = 'http://www.tfl.gov.uk/tfl/syndication/widgets/tubemap/default-search.html';
var iframe='<iframe id="tfl_tubemap_stretchy" name="tfl_tubemap" src ="#" width="100%" height="1" marginheight="0" marginwidth="0" frameborder="no" scrolling="no"></iframe>';
document.write(iframe);

var aspectRatio = .65;

var myIframe = parent.document.getElementById("tfl_tubemap_stretchy");
var iframeWidth = myIframe.clientWidth;
myIframe.height = iframeWidth * aspectRatio;
myIframe.width = iframeWidth;

myIframe.src = filePath;
//var iframeWidth = myIframe.clientWidth - 8;
//myIframe.style.border = "4px solid #CCC";