def xmlString = """<?xml version="1.0" encoding="UTF-8"?>
<S38:manageRequest xmlns:S38="http://content-available-to-author-only.com/S38" xmlns:header="http://content-available-to-author-only.com/header/" xmlns:xsi="http://w...content-available-to-author-only...3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://content-available-to-author-only.com/xsd/ManageItem XSD/ManageItem.xsd">
<header:standardHeader>
<header:serviceAddressing>
<header:to>
<header:address>http://content-available-to-author-only.com/BLAHBLAH</header:address>
<header:contextItemList>
<header:contextItem contextName="Channel" contextId="http://content-available-to-author-only.com/contextItem">I Need This</header:contextItem>
<header:contextItem contextName="Box" contextId="http://content-available-to-author-only.com/contextItem">Blue</header:contextItem>
</header:contextItemList>
</header:to>
</header:serviceAddressing>
</header:standardHeader>
</S38:manageRequest>"""
def xml = new XmlSlurper().parseText(xmlString)
def cItemChannel = xml.'**'.find {it.name() == 'contextItem' && it.@contextName == 'Channel'}?.text()
println cItemChannel
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