Blackout is not glamorous, but few small changes make as much difference to sleep. Light is the body's strongest signal to wake, and the early-morning glow through a gap in the curtains can end a nap, or a lie-in, before it has begun.

Why it matters

Darkness supports the natural sleep hormones that help everyone settle and stay asleep. It is especially useful for daytime naps and for the bright early mornings of a British summer, when 4.30am light can quietly undo an otherwise good night.

Getting it actually dark

• Mind the edges. Most light sneaks in around the sides, not through the fabric.
• Layer if you need to: a blind plus a lined curtain.
• A portable blackout blind travels well and saves many a holiday nap.

Test it in daylight. If you can comfortably read in the room, it is not blackout yet.