Access to the records in the featured collections from Ancestry, including all the census records, will be free until Monday 29 August 2016 at 23:59 BST -- 18.59 EDT.
The small print - to view these records you will need to register for free with Ancestry.co.uk with your name and email address. We will then send you a username and password to access the records. After the free access period ends, you will only be able to view the records in the featured collections using an Ancestry.co.uk paid membership. To see a full list of the records in the featured collections please click here.
I suspect there will be automatic access for ancestry.com and .ca subscribers.