public function isFieldVirtualised($field)
    {
        // Don't defer if field is non-virtualised
        $ignore = $this->getNonVirtualisedFields();
        if (in_array($field, $ignore)) {
            return false;
        }

        // Don't defer if no virtual page
        $copied = $this->CopyContentFrom();
        if (!$copied || !$copied->exists()) {
            return false;
        }

        // Check if copied object has this field
        return $copied->hasField($field);
    }