strip everything in front of body tag - regex help needed

I am trying to parse emails and strip everything before (And
including) the BODY tag of an html email/file.

So:
<html>
<title>blah</title>
<meta......
<body>
<b>this the body</b>
</body>
</html>

End result I want is just the:
<b>this is the body</b>

any recommendations on how to best do this in php?

Thanks!

.