To console myself, I bought lunch at the sushi shop next door, and also a bottle of fine Japanese green iced tea with nothing added and especially no sugar. And I thought, as I was coming back, that I have plenty of green tea teabags, and could get more green tea, easily enough, and that £1.95 was really quite a lot for what was essentially tea and water.
But how to make cold, refreshing, green tea, using only the tools I have in the office? Google finds lots of arguments. I should add that instant iced teas are available in the UK, but last I saw they all had either sugar or sweeteners, and I am a bitter drinker.
The tools in the office, incidentally, consist of:
A source of nearly boiling filtered water.
A source of chilled filtered water.
Hot and cold taps.
A microwave oven.
A large mug.
A plastic 500ml bottle that once contained green tea.