Runs from today until the 31st August in NI and across the UK. The valid days it runs are Mondays. Tuesdays and Wednesdays. 1,500 restaurants are participating in NI. You dont need a voucher, just make sure the restaurant is participating and order food (alcohol is excluded from the discount). You get 50% off your bill up to a maximum of £10 per person. So order £20 of food and it will cost you £10 at the till, order £10 worth it will cost you £5 and so on.
Sounds like a great deal even if it is only Monday to Wednesday. Would be worth peoples while crossing the border to take advantage if they dont live too far away.