private void addHelpHtml(final HelpHTML helpHTML) {
        if (this.helpHTML != null) {
            throw new IllegalStateException("FormGroup can only contain one child HelpHTML widget. " +
                                            "Class: " + helpHTML.getClass().getName());
        }
        this.helpHTML = helpHTML;
        this.helpHTML.setStyleName(CLASS_NAME_FORM_GROUP_HELP);

        updateHelpButton();
//        // helpText trumps helpHTML
//        if (NullSafe.isBlankString(helpText)) {
//            this.helpText = this.helpHTML.getHTML();
//        }
    }
Plain text, any HTML will be escaped.
The helpText attr trumps the {@code <form:HelpHTML>} element.
<p>
To programmatically set HTML help text, use {@link FormGroup#overrideHelpText(SafeHtml)}.
</p>
stroom-core-client-widget/src/main/java/stroom/widget/form/client/FormGroup.java