anchor.diff:      <p>Number 10 has 3 overlapping functions. It is the official residence of the British Prime Minister: it is their office, and it is also the place where the Prime Minister entertains guests from Her Majesty The Queen to presidents of the United States and other world leaders. The Prime Minister hosts countless receptions and events for a whole range of British and overseas guests, with charitable receptions high up the list.</p>
       <p>The building is much larger than it appears from its frontage. The hall with the chequered floor immediately behind the front door lets on to a warren of rooms and staircases. The house in Downing Street was joined to a more spacious and elegant building behind it in the early 18th century. Number 10 has also spread itself out to the left of the front door, and has taken over much of 12 Downing Street, which is accessed by a corridor that runs through 11 Downing Street &ndash; the official residence of the Chancellor of the Exchequer.</p>
   
  -    <h2 id="take-the-tour">Take the tour</h2>
  +    <h2 id="take-the-tour">Explore 10 Downing Street</h2>
  +    <p>Take a virtual tour inside 10 Downing Street.</p>
       <div class="virtual-tour js-virtual-tour">
         <div class="tour-nav">
           <ul>
  
positive.code:       <h1>Contents</h1>
        <ol>
          <li><a href="#introduction">Introduction</a></li>
          <li><a href="#take-the-tour">Take the tour</a></li>
          <li><a href="#origins-and-early-inhabitants">Origins and Early Inhabitants</a></li>
          <li><a href="#emergence-of-downing-street">The Emergence of Downing Street</a></li>
          <li><a href="#pelham-to-pitt">Pelham to Pitt</a></li>
  
negative.code:         </div>
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      <p>Explore 10 Downing Street's most famous rooms and significant events in more detail at the <a href="https://www.google.com/culturalinstitute/beta/u/0/partner/10-downing-street">Google Cultural Institute</a>.</p>
  
      <h2 id="origins-and-early-inhabitants">Origins and early inhabitants</h2>
      <p>The area around Downing Street was home to ancient Roman, Anglo-Saxon and Norman settlements, and was already a prestigious centre of government 1,000 years ago.</p>
  