For a large gathering, tea can be kept coming by brewing in rotation with two teapots: while one is served, the other brews, so every cup gets fresh tea. Keep hot water in the kettle, and dilute the brew by the same amount in every cup. If a single large teapot sits for a long time, the tea gets bitter, and the last cups come out darker and stronger than the first.
The challenge of serving tea to a large group is timing, not quantity. If one large teapot is brewed once and used throughout the gathering, the tea grows darker and more bitter as it sits; the first cups taste fine, while the last are astringent and strong. That is why it is recommended to brew fresh tea instead of letting the dark tea at the bottom of the teapot sit for too long. The way to do this for a large group is not to use one bigger teapot, but to rotate the brews. The larger the gathering, the sooner this difference becomes noticeable, because the tea sits longer as serving goes on.
Set up the rotation with two teapots. Once the first teapot is brewed, begin serving; at the same time, put tea in the second teapot and pour water over it. The recommended steeping time for black tea is 4–6 minutes with water at 90–95°C / 194–203°F; serve from the first teapot during that time, and the second will be ready just as the first runs out. When the first teapot is empty, discard the old brewed tea at the bottom, rinse the pot, refill it, and put it at the end of the rotation. This way, tea that has been sitting for a long time is never served. If the same amount of tea is put in both teapots, the flavor will stay the same as the rotation changes.
Keep hot water under the two teapots at all times. Keep a large kettle full over low heat so water is always ready to pour into a teapot or a cup. When the kettle is half empty, refill it instead of letting it run dry; having to boil the kettle again would make the guests wait. The teapots stay warm from the steam when placed on the kettle, but they should not be set over the kettle’s direct flame; boiling the tea makes it bitter. Keep the heat under the kettle on throughout the gathering, just turned low.
Pour the brewed tea into each cup first, then add water. If the amount of brewed tea is the same in every cup, everyone gets the same tea whether they prefer it light or strong; only the added water changes. To do this, tilt the teapot from the same height for the same amount of time, using the same point in the cup as a visual measure. Ask guests at the start whether they prefer light or strong tea, then arrange the cups in two rows on the tray so they do not get mixed up. Serve sugar and lemon on a separate plate, not in the tea. Put a saucer under each cup on the tray so it can be held while the hot cup is passed from hand to hand.
Plan the pace of service too. Take cups to the table a full tray at a time, not all in 1 trip; collect empty cups on the same tray and refill them. Replace a half-full cup left to cool at the table with a fresh one; do not top it up with hot tea, because mixing cooled tea with fresh tea spoils the flavor. If one person is assigned only to serving tea, the host does not have to leave the table, and the two-teapot rotation continues without interruption. Keep one of the teapots full until the last guest leaves so even a late-arriving guest gets fresh tea.