public function addMethod($method)
    {
        // Capitalise method
        $method = strtoupper($method);

        if (!in_array($method, self::$availableMethods)) {
            throw new InvalidArgumentException(sprintf('Invalid method for route with path "%s". Method must be one of: ' . implode(', ', self::$availableMethods) . '. Got "%s" instead.', $this->getPath(), $method));
        }

        if (!in_array($method, $this->methods)) {
            $this->methods[] = $method;
        }

        // Add HEAD method if GET has been allowed for this Route
        if ($method == 'GET') {
            $this->addMethod('HEAD');
        }

        return $this;
    }