XML string element that contains XML tags within the value text

I want to have a string element with the following contents:

<UmlMessage>"@MainApp -> ControlThread : <font color=red><b>NET_SET_REQ</b>"</UmlMessage>

So the element UmlMessage value will be: "@MainApp -> ControlThread : <font color=red><b>NET_SET_REQ</b>"

I added the quotes, but that did not help. I get a strange error:

XMLSyntaxError: AttValue: " or ' expected, line 25, column 54

I assume it is to do with having XML-like tags in the value. But I want what is between the tags to be parsed as a string literal... is that possible?