T5: XML encoding of URLs

[Szemere Szemere]

I'm having trouble including an image source URL in my .tml files. The URL
has & and ? characters in it. If I use &, then the T5 XML validation
complains that I have unterminated entities (not surprising). However if I
replace & with & (ampersand-"amp"-semicolon) then the whole 5 character
string gets passed through to the browser (ie. not XML decoded), which is
surprising.  Any obvious way to handle this?

Snippet of the code
<img src="http://chart.apis.google.com/chart&amp;quest;chs=800x300"; />

I'm on T5.0.7.