We all know about their double cheeseburger for just £1.49 but they will let you add as many 'pattys' as you like on top (within reason!) for just 60p each.
This is advertised on a white background under their main menu with "How many can you handle".
£2.19 for a triple cheeseburger!
This offer was originally for the XL burgers and those are £1 for each extra burger but we don't care about that.
Swindon told me they won't put more than 15 in one bun.
Here is the original post that I did last year with the brilliant picture of a burger from Hong Kong Burger King - http://www.hotukdeals.com/deals/1-29-double-cheeseburger-pay-just-60p-for-each-extra-burger-one-bun-burger-king-2428606#comments