Hidden Field not sending default value.

Hi,
I am trying to use a hidden field to identify which website my form gets sent from.
The field does not show on the form as there is no data input required from the user.

I am using the Mailchimp extension.
The Mailchimp custom field is: LEADSOURCE
The Contact Form value is [Lead source]

The line I am using is:
[hidden your-leadsource default:Lead Source “computerfranchise.co.uk”]
I am getting the result [Lead source] in Mailchimp.

If I change the line to:
[hidden your-leadsource default:omputerfranchise.co.uk]
The result I get in Mailchimp is still [Lead source]

Any ideas what I am missing?

Thanks