I've heard about an offer for gbk where if you buy one burger, you get a second for £1. Any ideas where I can get hold of the voucher for this?

I've heard about an offer for gbk where if you buy one burger, you get a second for £1.  Any ideas where I can get hold of the voucher for this?

Hi this message has probably come abit too late but you can get the offer here tinyurl.com/yjxyunv

it is still valid until the 7th Feb.

It's alright....a found a voucher for this a few days after posting and we had a lovely meal! Thanks anyway!