Mapping our API tokens to Tyk's tokens (SOLVED)

Ok, so I tried submitting the following (obviously replacing the authorization key with the one for my own user - which I also set as admin, and also putting the correct API key for the API I have created in the system).

 curl -X POST -H "authorization: 1238b7e0e2ff4c2957321724409ee2eb" \
     -s \
     -H "Content-Type: application/json" \
     -X PUT \
     -d '{
        "allowance": 1000,
        "rate": 1000,
        "per": 1,
        "expires": -1,
        "quota_max": -1,
        "quota_renews": 1449051461,
        "quota_remaining": -1,
        "quota_renewal_rate": 60,
        "access_rights": {
            "ad5004d961a147d4649fd3216694ebe2": {
                "api_id": "ad5004d961a147d4649fd3216694ebe2",
                "api_name": "test-api",
                "versions": ["Default"]
            }
        },
        "meta_data": {}
     }' http://admin.cloud.tyk.io/api/keys/abcde1234567 | python -mjson.tool

However, I am getting the following error:

{
    "Message": "Attempted access to non-owned key",
    "Meta": null,
    "Status": "Error"
}

What am I doing wrong?