Basic work version:
1. Take one wire-mesh tea-strainer spoon, and insert one good teaspoon of Keemun Black tea (Twinings Prince of Wales at a pinch).
2. Nuke water in big mug in industrial-strength microwave oven until it really boils
3. Add tea-strainer spoon.
4. Infuse as long as desired, or alternatively forget about it whilst coding and drink arbitrarily strong
4b) add milk and sugar if you must
Keemun black tea is very dark by nature, and never turns bitter, so forgetting to remove the tea only makes it stronger, but never renders it undrinkable.
On the road version:
replace tea strainer egg by Twinings Prince of Wales tea bags
Working in region with hard water:
Replace Keemun Black by good quality Assam and keep infusion time down. Assam takes hard water better than most