Saw it for £2.99 (cheapest I can find as they usually go for £3.99+) and noticed it was Buy One Get One Half Price! Meaning £4.48 for two!
Simply add multiples of 2 to the basket. Available for click and collect from certain branches in England. I ordered 16 at a cost of £35.84 so I could get free delivery (on orders over £35) :P