This works fine for me:
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>HTML in SVG in HTML</title>
<style type="text/css">
svg { border: 1px solid black; }
svg div { border: 1px dotted blue; }
</style>
</head>
<body>
<svg xmlns="http://www.w3.org/2000/svg" width="800" height="500">
<foreignObject class="node" x="46" y="22" width="200" height="300">
<body xmlns="http://www.w3.org/1999/xhtml">
<div>The quick brown fox jumps over the lazy dog. Pack my box with
five dozen liquor jugs</div>
</body>
</foreignObject>
</svg>
</body>
</html>