You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allimages gaicontinue="Feltham_Station_Post_Box_Demystified_digraph_postbox_Andy.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1569" ns="6" title="File:2012-10-11-redacted-complaint-to-tesco-regarding-failed-deliveries.pdf" />
      <page pageid="1873" ns="6" title="File:Arnie.png" />
      <page pageid="1376" ns="6" title="File:Buggered graph.png" />
      <page pageid="1332" ns="6" title="File:Cacti favicon.ico" />
      <page pageid="1331" ns="6" title="File:Cacti favicon demo.png" />
      <page pageid="1433" ns="6" title="File:DSCF7787 copy.jpg" />
      <page pageid="1881" ns="6" title="File:Disk layout digraph layout.png" />
      <page pageid="1890" ns="6" title="File:Dog Show Poster.pdf" />
      <page pageid="1379" ns="6" title="File:Fairytale gwb cheney duet.txt" />
      <page pageid="1885" ns="6" title="File:Feltham Station Post Box Demystified digraph postbox.png" />
    </pages>
  </query>
</api>