diff --git a/app/assets/javascripts/detailsPolyfill.js b/app/assets/javascripts/detailsPolyfill.js
deleted file mode 100644
index ce0692195..000000000
--- a/app/assets/javascripts/detailsPolyfill.js
+++ /dev/null
@@ -1,196 +0,0 @@
-// From
-// https://github.com/alphagov/govuk_elements/blob/4926897dc7734db2fc5e5ebb6acdc97f86e22e50/public/javascripts/vendor/details.polyfill.js
-//
-// ---
-//
-// <details> polyfill
-// http://caniuse.com/#feat=details
-
-// FF Support for HTML5's <details> and <summary>
-// https://bugzilla.mozilla.org/show_bug.cgi?id=591737
-
-// http://www.sitepoint.com/fixing-the-details-element/
-
-(function () {
-  'use strict';
-
-  var NATIVE_DETAILS = typeof document.createElement('details').open === 'boolean';
-
-  // Add event construct for modern browsers or IE
-  // which fires the callback with a pre-converted target reference
-  function addEvent(node, type, callback) {
-    if (node.addEventListener) {
-      node.addEventListener(type, function (e) {
-        callback(e, e.target);
-      }, false);
-    } else if (node.attachEvent) {
-      node.attachEvent('on' + type, function (e) {
-        callback(e, e.srcElement);
-      });
-    }
-  }
-
-  // Handle cross-modal click events
-  function addClickEvent(node, callback) {
-    // Prevent space(32) from scrolling the page
-    addEvent(node, 'keypress', function (e, target) {
-      if (target.nodeName === 'SUMMARY') {
-        if (e.keyCode === 32) {
-          if (e.preventDefault) {
-            e.preventDefault();
-          } else {
-            e.returnValue = false;
-          }
-        }
-      }
-    });
-    // When the key comes up - check if it is enter(13) or space(32)
-    addEvent(node, 'keyup', function (e, target) {
-      if (e.keyCode === 13 || e.keyCode === 32) { callback(e, target); }
-    });
-    addEvent(node, 'mouseup', function (e, target) {
-      callback(e, target);
-    });
-  }
-
-  // Get the nearest ancestor element of a node that matches a given tag name
-  function getAncestor(node, match) {
-    do {
-      if (!node || node.nodeName.toLowerCase() === match) {
-        break;
-      }
-    } while ((node = node.parentNode));
-
-    return node;
-  }
-
-  // Create a started flag so we can prevent the initialisation
-  // function firing from both DOMContentLoaded and window.onload
-  var started = false;
-
-  // Initialisation function
-  function addDetailsPolyfill(list) {
-
-    // If this has already happened, just return
-    // else set the flag so it doesn't happen again
-    if (started) {
-      return;
-    }
-    started = true;
-
-    // Get the collection of details elements, but if that's empty
-    // then we don't need to bother with the rest of the scripting
-    if ((list = document.getElementsByTagName('details')).length === 0) {
-      return;
-    }
-
-    // else iterate through them to apply their initial state
-    var n = list.length, i = 0;
-    for (i; i < n; i++) {
-      var details = list[i];
-
-      // Save shortcuts to the inner summary and content elements
-      details.__summary = details.getElementsByTagName('summary').item(0);
-      details.__content = details.getElementsByTagName('div').item(0);
-
-      // If the content doesn't have an ID, assign it one now
-      // which we'll need for the summary's aria-controls assignment
-      if (!details.__content.id) {
-        details.__content.id = 'details-content-' + i;
-      }
-
-      // Add ARIA role="group" to details
-      details.setAttribute('role', 'group');
-
-      // Add role=button to summary
-      details.__summary.setAttribute('role', 'button');
-
-      // Add aria-controls
-      details.__summary.setAttribute('aria-controls', details.__content.id);
-
-      // Set tabIndex so the summary is keyboard accessible for non-native elements
-      // http://www.saliences.com/browserBugs/tabIndex.html
-      if (!NATIVE_DETAILS) {
-        details.__summary.tabIndex = 0;
-      }
-
-      // Detect initial open state
-      var openAttr = details.getAttribute('open') !== null;
-      if (openAttr === true) {
-        details.__summary.setAttribute('aria-expanded', 'true');
-        details.__content.setAttribute('aria-hidden', 'false');
-      } else {
-        details.__summary.setAttribute('aria-expanded', 'false');
-        details.__content.setAttribute('aria-hidden', 'true');
-        if (!NATIVE_DETAILS) {
-          details.__content.style.display = 'none';
-        }
-      }
-
-      // Create a circular reference from the summary back to its
-      // parent details element, for convenience in the click handler
-      details.__summary.__details = details;
-
-      // If this is not a native implementation, create an arrow
-      // inside the summary
-
-      var twisty = document.createElement('i');
-
-      if (openAttr === true) {
-        twisty.className = 'arrow arrow-open';
-        twisty.appendChild(document.createTextNode('\u25bc'));
-      } else {
-        twisty.className = 'arrow arrow-closed';
-        twisty.appendChild(document.createTextNode('\u25ba'));
-      }
-
-      details.__summary.__twisty = details.__summary.insertBefore(twisty, details.__summary.firstChild);
-      details.__summary.__twisty.setAttribute('aria-hidden', 'true');
-
-    }
-
-    // Define a statechange function that updates aria-expanded and style.display
-    // Also update the arrow position
-    function statechange(summary) {
-
-      var expanded = summary.__details.__summary.getAttribute('aria-expanded') === 'true';
-      var hidden = summary.__details.__content.getAttribute('aria-hidden') === 'true';
-
-      summary.__details.__summary.setAttribute('aria-expanded', (expanded ? 'false' : 'true'));
-      summary.__details.__content.setAttribute('aria-hidden', (hidden ? 'false' : 'true'));
-
-      if (!NATIVE_DETAILS) {
-        summary.__details.__content.style.display = (expanded ? 'none' : '');
-
-        var hasOpenAttr = summary.__details.getAttribute('open') !== null;
-        if (!hasOpenAttr) {
-          summary.__details.setAttribute('open', 'open');
-        } else {
-          summary.__details.removeAttribute('open');
-        }
-      }
-
-      if (summary.__twisty) {
-        summary.__twisty.firstChild.nodeValue = (expanded ? '\u25ba' : '\u25bc');
-        summary.__twisty.setAttribute('class', (expanded ? 'arrow arrow-closed' : 'arrow arrow-open'));
-      }
-
-      return true;
-    }
-
-    // Bind a click event to handle summary elements
-    addClickEvent(document, function(e, summary) {
-      if (!(summary = getAncestor(summary, 'summary'))) {
-        return true;
-      }
-      return statechange(summary);
-    });
-  }
-
-  // Bind two load events for modern and older browsers
-  // If the first one fires it will set a flag to block the second one
-  // but if it's not supported then the second one will fire
-  addEvent(document, 'DOMContentLoaded', addDetailsPolyfill);
-  addEvent(window, 'load', addDetailsPolyfill);
-
-})();