Heathrow runs four main passenger terminals these days. Terminals 2 and 3 sit close together in the central area and you can walk between them landside through a covered link. Terminal 4 sits off to the south on its own and Terminal 5 is out at the western edge with its own satellite buildings. Knowing which one you need before you arrive already cuts a lot of the confusion.

For connections on the same ticket the free Flight Connections coach runs airside between all terminals every few minutes. Follow the purple signs after you land and it drops you near the next departure area. If your bags are checked through you often stay airside the whole way. Separate tickets usually mean collecting luggage, clearing border control and starting again from check-in, so build in extra time for that.

Landside transfers work best on the trains. The short hop between the central terminals and Terminal 5 takes about six minutes on the express service. The Elizabeth line and Piccadilly line also link everything, though they can feel busier at peak hours. Walking is realistic only between 2 and 3.

Security is the usual UK setup. Liquids under 100 ml in a clear bag, laptops and tablets out of the bag, jackets off. Queues move faster if you have everything ready before you reach the trays. Early morning and late evening are quieter than midday. If you have a tight connection head straight for the transfer security lanes rather than the main ones.

Long layovers feel easier once you leave the main shopping halls. In Terminal 5 the seating behind some of the larger retail areas near the A gates stays calmer. Terminal 2 satellite gates reached by the short underground walkway are often quieter and have big windows. Look for corners away from the food courts and boarding calls. A few benches without armrests make it possible to stretch out if you need a rest. Bring a light scarf or eye mask and keep your bag in sight.

Give yourself more buffer than the minimum connection time, especially if you have to change terminals or clear immigration. Check the screens early for any gate changes and you will move through with far less rush.