diff --git a/README.md b/README.md
index 04f69f0..82a0321 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,10 @@ Further data can be loaded from YAML fixtures or database dumps.
 The session is persisted in a file which is generated upon starting the session.
 As long as this file exists, the test session is considered in progress,
 both in web browsers and command-line execution. By default, the file
-is stored in the webroot under `TESTS_RUNNING.js`.
+is stored in the webroot under `TESTS_RUNNING-<id>.js`. The `<id>` value
+is a random token stored in the browser session, in order to make the
+test session specific to the executing browser, and allow multiple
+people using their own test session in the same webroot.
 
 The module also serves as an initializer for the
 [SilverStripe Behat Extension](https://github.com/silverstripe-labs/silverstripe-behat-extension/).
diff --git a/_config/_config.yml b/_config/_config.yml
index 75ffce3..425ffd9 100644
--- a/_config/_config.yml
+++ b/_config/_config.yml
@@ -5,9 +5,4 @@ Injector:
   RequestProcessor:
     properties:
       filters:
-        - '%$TestSessionRequestFilter'
----
-Name: testsession-setup
----
-TestSessionEnvironment:
-  test_state_file: TESTS_RUNNING.json
\ No newline at end of file
+        - '%$TestSessionRequestFilter'
\ No newline at end of file
diff --git a/code/TestSessionController.php b/code/TestSessionController.php
index 79d68be..3384054 100644
--- a/code/TestSessionController.php
+++ b/code/TestSessionController.php
@@ -30,7 +30,7 @@ class TestSessionController extends Controller {
 	public function __construct() {
 		parent::__construct();
 
-		$this->environment = Injector::inst()->get('TestSessionEnvironment');
+		$this->environment = Injector::inst()->get('TestSessionEnvironment', Session::get('TestSessionId'));
 	}
 
 	public function init() {
@@ -68,6 +68,10 @@ class TestSessionController extends Controller {
 	public function start() {
 		$params = $this->request->requestVars();
 
+		$generator = Injector::inst()->get('RandomGenerator');
+		$id = substr($generator->randomToken(), 0, 10);
+		Session::set('TestSessionId', $id);
+
 		// Convert datetime from form object into a single string
 		$params = $this->fixDatetimeFormField($params);
 
@@ -83,7 +87,7 @@ class TestSessionController extends Controller {
 			)
 		);
 
-		$this->environment->startTestSession($params);
+		$this->environment->startTestSession($params, $id);
 		
 		return $this->renderWith('TestSession_inprogress');
 	}
@@ -255,6 +259,7 @@ class TestSessionController extends Controller {
 		}
 
 		$this->environment->endTestSession();
+		Session::clear('TestSessionId');
 
 		// Clear out all PHP session states which have been set previously
 		if($sessionStates = Session::get('_TestSessionController.BrowserSessionState')) {
diff --git a/code/TestSessionEnvironment.php b/code/TestSessionEnvironment.php
index 1cbbec8..32e6f21 100644
--- a/code/TestSessionEnvironment.php
+++ b/code/TestSessionEnvironment.php
@@ -43,7 +43,13 @@ class TestSessionEnvironment extends Object {
 	 * @var string Path (from web-root) to the test state file that indicates a testsession is in progress.
 	 * Defaults to value stored in testsession/_config/_config.yml
 	 */
-	private static $test_state_file;
+	private static $test_state_file = 'TESTS_RUNNING.json';
+
+	/**
+	 * @config
+	 * @var [type]
+	 */
+	private static $test_state_id_file = 'TESTS_RUNNING-%s.json';
 
 	public function __construct($id = null) {
 		parent::__construct();
@@ -84,6 +90,7 @@ class TestSessionEnvironment extends Object {
 	 */
 	public function startTestSession($state, $id = null) {
 		$this->removeStateFile();
+		$this->id = $id;
 
 		$extendedState = $this->extend('onBeforeStartTestSession', $state);
 
diff --git a/code/TestSessionRequestFilter.php b/code/TestSessionRequestFilter.php
index f672af1..cc3cc21 100644
--- a/code/TestSessionRequestFilter.php
+++ b/code/TestSessionRequestFilter.php
@@ -10,7 +10,10 @@ class TestSessionRequestFilter {
 	protected $testSessionEnvironment;
 
 	public function __construct() {
-		$this->testSessionEnvironment = Injector::inst()->get('testSessionEnvironment');
+		$this->testSessionEnvironment = Injector::inst()->get(
+			'TestSessionEnvironment',
+			Session::get('TestSessionId')
+		);
 	}
 	
 	public function preRequest($req, $session, $model) {