I explained to him - as I withdrew the cup, ripped open the sachet and dunked the tea bag - that tea was an infusion, which meant that it was vital for the water to be actually boiling when it came into contact with the leaves. He looked at me furiously... I had behaved like this many times before: taking Canute's stance in the path of the great surge of ill-brewed tepid tea that was inundating England.