Saw this today in the ASDA in Harpurhey, Manchester. Thought it was a good deal.
I know you can normally get it cheap in Wilkinsons and Superdrug but if you can't be bothered going there or your doing your shopping at asda it's convinient!
Have checked online and it's not £4 but asda are having some offers on toiletries instore at the moment.
1L VALUE PACK. Reduced plaque by up to 56% more than brushing alone. USED TWICE DAILY, COOLMINT LISTERINE PROVIDES 24 HOUR PROTECTION AGAINST PLAQUE AND LASTING FRESH BREATH CONFIDENCE. COOLMINT LISTERINE IS CLINICALLY PROVEN TO: Prevent & reduce plaque, a major cause of gum disease. Kill bacteria between teeth. Freshen breath.