Json-in-script - can't get results!

Dear all,
I think this may be the wrong forum but cannot find one for the Places API, so apologies.

I'm having a problem trying to dowload Places information via json-in script.
This code (taken from the google documentation (http://code.google.com/apis/gdata/docs/json.html)) works for me:

<script type ="text/javascript">
function testthis(source){
alert("the test worked");
}
</script>

<script src="http://www.google.com/calendar/feeds/developer-calendar*at sign*google.com/public/full?alt=json-in-script&callback=listEvents">
</script>
(please replace *at sign* with an @.
However when I swap the code to a Places search, the code doesn't work:

<script type ="text/javascript">
function testthis(source){
alert("the test worked");
}
</script>

<script src="https://maps.googleapis.com/maps/api/place/search/alt=json-in-script?location=51.1814267,-0.0201796&radius=1000&types=food&sensor=false&key=AIzaSyA79UbGT0q1TxYnUIZ7A19GW3Nm1TKnqAE&callback=testthis"></script>

When go to the URL:
https://maps.googleapis.com/maps/api/place/search/json?location=51.1814267,-0.0201796&radius=1000&types=food&sensor=false&key=AIzaSyA79UbGT0q1TxYnUIZ7A19GW3Nm1TKnqAE&callback=testthis

I get a JSON results (have highlighted the only change I made), so the problem must lie with the "alt=json-in-script" part, but for the life of me I can't figure out where.

Can anybody help me please, I would be very very grateful!