The offer is advertised as two Yorkshire Tea 80 bag boxes for £3. But once scanned through at the till the cost is £2. This was at my local Morrisons store but I assume the offer is nation wide.
Individually the 80 bag boxes cost £2.28, so you getting 28p off and a free box.
The offer applies to the Original, Hard Water, Gold and Decaffinated varieties of the 80 bag boxes. I personally bought two boxes of Hard Water tea but i would assume any combination should work.
I cannot remember when the offer ends so have set the expiry to the end of may.