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>
    <allfileusages afcontinue="Lamp_tavern_ls.jpg|44" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:Birmingham-conservatoire01.jpg" />
      <f ns="6" title="File:Cafe ort img 5455-2.jpg" />
      <f ns="6" title="File:Club db.jpg" />
      <f ns="6" title="File:Eagle inn salford.jpg" />
      <f ns="6" title="File:EarCleaning.jpg" />
      <f ns="6" title="File:Eggtimer ballo tacettop crop2.png" />
      <f ns="6" title="File:Greenhouse p1010117.jpg" />
      <f ns="6" title="File:Gregson-lg.jpg" />
      <f ns="6" title="File:Harehounds Venue-1.jpg" />
      <f ns="6" title="File:Imagename.jpg" />
    </allfileusages>
  </query>
</api>