Indentifying the SOAP version

When working with a SOAP message, how can I tell which version of SOAP it is? The SOAP envelope’s namespace indicates the SOAP version.

SOAP 1.1:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
  <soapenv:Header/>
  <soapenv:Body/>
</soapenv:Envelope>

SOAP 1.2:

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
  <soap:Header/>
  <soap:Body/>
</soap:Envelope>