I think this must be by e-mail link referral, but keep your heads up for it.
Free 1.000 Nectar points for clicking a link, not bad!
EDIT (This is the only info on the site after clicking on the link):
Bonus Nectar points will be added only to the balance of the recipient of the email, and must have been claimed by clicking through from the email to this page by 23.59 on Tuesday 13 December 2016. Only one bonus permitted per customer. Bonus Nectar points will be credited to your account on or before 20 December 2016. Promoter: Sainsbury's Supermarkets Ltd, 33 Holborn, London, EC1N 2HT.
---------- Seems like it had already been posted, marked as EXPIRED for that reason.