[web2py] web2py doesn't seem to be picking up posted json

[Matt Thompson]

I'm using the following function from the documentation for a RESTful web 
service

    def POST(table_name,**fields): 
        string = ""
        if table_name == 'person': 
            for key in fields:
                string = string + "another keyword arg: %s: %s" % (key, 
fields[key])
            return string
            #return db.t_person.validate_and_insert(fields) 
        elif table_name == 'pet': 
            return db.pet.validate_and_insert(**vars) 
        else: 
            raise HTTP(400)

The JSON that's being posted isn't being included in **fields, Some 
searching has lead me to information about the POST not being a key pair 
but just JSON so I wondered if web2py was struggling with that?

http://stackoverflow.com/questions/6702490/how-to-use-extjs4-save-in-php-server/6703326#6703326
 

The data being sent also includes data on the URL eg 
/api/person/?_dc=86876876

That is being returned in the response from the above function.

Any help appreciated.

Matt