diff --git a/javascripts/govuk/details.polyfill.js b/javascripts/govuk/details.polyfill.js
new file mode 100644
index 00000000..a1f1f711
--- /dev/null
+++ b/javascripts/govuk/details.polyfill.js
@@ -0,0 +1,240 @@
+// <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 (global) {
+  'use strict'
+
+  var GOVUK = global.GOVUK || {}
+
+  GOVUK.details = {
+    NATIVE_DETAILS: typeof document.createElement('details').open === 'boolean',
+    KEY_ENTER: 13,
+    KEY_SPACE: 32,
+
+    // Create a started flag so we can prevent the initialisation
+    // function firing from both DOMContentLoaded and window.onload
+    started: false,
+
+    // Add event construct for modern browsers or IE
+    // which fires the callback with a pre-converted target reference
+    addEvent: function (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)
+        })
+      }
+    },
+
+    removeEvent: function (node, type) {
+      if (node.removeEventListener) {
+        node.removeEventListener(type, function (e) {
+        }, false)
+      } else if (node.detachEvent) {
+        node.detachEvent('on' + type, function (e) {
+        })
+      }
+    },
+
+    // Cross-browser character code / key pressed
+    charCode: function (e) {
+      return (typeof e.which === 'number') ? e.which : e.keyCode
+    },
+
+    // Cross-browser preventing default action
+    preventDefault: function (e) {
+      if (e.preventDefault) {
+        e.preventDefault()
+      } else {
+        e.returnValue = false
+      }
+    },
+
+    // Handle cross-modal click events
+    addClickEvent: function (node, callback) {
+      GOVUK.details.addEvent(node, 'keypress', function (e, target) {
+        // When the key gets pressed - check if it is enter or space
+        if (GOVUK.details.charCode(e) === GOVUK.details.KEY_ENTER || GOVUK.details.charCode(e) === GOVUK.details.KEY_SPACE) {
+          if (target.nodeName.toLowerCase() === 'summary') {
+            // Prevent space from scrolling the page
+            // and enter from submitting a form
+            GOVUK.details.preventDefault(e)
+            // Click to let the click event do all the necessary action
+            if (target.click) {
+              target.click()
+            } else {
+              // except Safari 5.1 and under don't support .click() here
+              callback(e, target)
+            }
+          }
+        }
+      })
+
+      // Prevent keyup to prevent clicking twice in Firefox when using space key
+      GOVUK.details.addEvent(node, 'keyup', function (e, target) {
+        if (GOVUK.details.charCode(e) === GOVUK.details.KEY_SPACE) {
+          if (target.nodeName === 'SUMMARY') {
+            GOVUK.details.preventDefault(e)
+          }
+        }
+      })
+
+      GOVUK.details.addEvent(node, 'click', function (e, target) {
+        callback(e, target)
+      })
+    },
+
+    // Get the nearest ancestor element of a node that matches a given tag name
+    getAncestor: function (node, match) {
+      do {
+        if (!node || node.nodeName.toLowerCase() === match) {
+          break
+        }
+        node = node.parentNode
+      } while (node)
+
+      return node
+    },
+
+    // Initialisation function
+    addDetailsPolyfill: function (list, container) {
+      container = container || document.body
+      // If this has already happened, just return
+      // else set the flag so it doesn't happen again
+      if (GOVUK.details.started) {
+        return
+      }
+      GOVUK.details.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 = container.getElementsByTagName('details')).length === 0) {
+        return
+      }
+      // else iterate through them to apply their initial state
+      var n = list.length
+      var 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 (!details.__summary || !details.__content) {
+          return
+        }
+        // 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 (!GOVUK.details.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 (!GOVUK.details.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
+        if (!GOVUK.details.NATIVE_DETAILS) {
+          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')
+        }
+      }
+
+      // Bind a click event to handle summary elements
+      GOVUK.details.addClickEvent(container, function (e, summary) {
+        if (!(summary = GOVUK.details.getAncestor(summary, 'summary'))) {
+          return true
+        }
+        return GOVUK.details.statechange(summary)
+      })
+    },
+
+    // Define a statechange function that updates aria-expanded and style.display
+    // Also update the arrow position
+    statechange: function (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 (!GOVUK.details.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
+    },
+
+    destroy: function (node) {
+      GOVUK.details.removeEvent(node, 'click')
+    },
+
+    // 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
+    init: function ($container) {
+      GOVUK.details.addEvent(document, 'DOMContentLoaded', GOVUK.details.addDetailsPolyfill)
+      GOVUK.details.addEvent(window, 'load', GOVUK.details.addDetailsPolyfill)
+    }
+  }
+  global.GOVUK = GOVUK
+})(window)
diff --git a/spec/manifest.js b/spec/manifest.js
index 9ab0cb12..5c9d41ec 100644
--- a/spec/manifest.js
+++ b/spec/manifest.js
@@ -2,6 +2,7 @@
 var manifest = {
   support: [
     '../../node_modules/jquery/dist/jquery.js',
+    '../../javascripts/govuk/details.polyfill.js',
     '../../javascripts/govuk/modules.js',
     '../../javascripts/govuk/modules/auto-track-event.js',
     '../../javascripts/govuk/primary-links.js',
@@ -19,6 +20,7 @@ var manifest = {
     '../../javascripts/govuk/analytics/mailto-link-tracker.js'
   ],
   test: [
+    '../unit/details.polyfill.spec.js',
     '../unit/modules.spec.js',
     '../unit/Modules/auto-track-event.spec.js',
     '../unit/primary-links.spec.js',
diff --git a/spec/unit/details.polyfill.spec.js b/spec/unit/details.polyfill.spec.js
new file mode 100644
index 00000000..b223ab3e
--- /dev/null
+++ b/spec/unit/details.polyfill.spec.js
@@ -0,0 +1,91 @@
+/* global describe it expect beforeEach afterEach */
+
+var $ = window.jQuery
+
+describe('details-polyfill', function () {
+  'use strict'
+  var GOVUK = window.GOVUK
+
+  beforeEach(function (done) {
+    // Sample markup
+    this.$content = $(
+      '<details>' +
+      '<summary><span class="summary">Summary</span></summary>' +
+      '<div><p>Hidden content</p></div>' +
+      '</details>'
+    )
+
+    // Find elements
+    var $summaries = this.$content.find('summary')
+    var $hiddenContent = this.$content.find('div')
+
+    this.$summary1 = $summaries.eq(0)
+    this.$hiddenContent1 = $hiddenContent.eq(0)
+
+    // Add to page
+    $(document.body).append(this.$content)
+
+    setTimeout(function () {
+      done()
+    }, 1)
+  })
+
+  afterEach(function () {
+    this.detailsPolyfill = null
+    this.$content.remove()
+  })
+
+  describe('When the polyfill is initialised', function () {
+    beforeEach(function () {
+      // Initialise detailsPolyfill
+      this.detailsPolyfill = GOVUK.details.addDetailsPolyfill()
+      GOVUK.details.started = false
+    })
+    it('should add to summary the button role', function () {
+      expect(this.$summary1.attr('role')).toBe('button')
+    })
+
+    it('should set the element controlled by the summary using aria-controls', function () {
+      expect(this.$summary1.attr('aria-controls')).toBe('details-content-0')
+    })
+
+    it('should set the expanded state of the summary to false using aria-expanded', function () {
+      expect(this.$summary1.attr('aria-expanded')).toBe('false')
+    })
+
+    it('should add a unique id to the hidden content in order to be controlled by the summary', function () {
+      expect(this.$hiddenContent1.attr('id')).toBe('details-content-0')
+    })
+
+    it('should present the content as hidden using aria-hidden', function () {
+      expect(this.$hiddenContent1.attr('aria-hidden')).toBe('true')
+    })
+
+    it('should visually hide the content', function () {
+      expect(this.$hiddenContent1.is(':visible')).toBe(false)
+    })
+
+    describe('and when summary is clicked', function () {
+      beforeEach(function () {
+        // Trigger click on summary
+        this.$summary1.click()
+      })
+
+      it('should indicate the expanded state of the summary using aria-expanded', function () {
+        expect(this.$summary1.attr('aria-expanded')).toBe('true')
+      })
+
+      it('should make the content visible', function () {
+        expect(this.$hiddenContent1.is(':visible')).toBe(true)
+      })
+
+      it('should indicate the visible state of the content using aria-hidden', function () {
+        expect(this.$hiddenContent1.attr('aria-hidden')).toBe('false')
+      })
+
+      it('should indicate the open state of the content', function () {
+        expect(this.$content.attr('open')).toBe('open')
+      })
+    })
+  })
+})