Add string to XML Message - HTTP Post

Hi experts,

I have a requirement to modify a XML payload and add a test string to the start. The usual XML payload is below

<?xml version="1.0" encoding="UTF-8"?>

<Request version="1.0">

<Verification>123</Verification>

</Request>

What I want to do is add a test string to the start of the XML payload as shown below.

load=<?xml version="1.0" encoding="UTF-8"?>

<Request version="1.0">

<Verification>123</Verification>

</Request>

Does anyone have any ideas how this can be done?