The basics
London to Tokyo is a nine-hour eastbound shift, one of the more demanding adjustments for British travellers. Direct flights take around 11 to 12 hours, typically departing London in the morning and arriving in Tokyo in the early morning the following day. When you land at 8am Tokyo time, your body thinks it's 11pm the night before. You've skipped a night's sleep and your clock is nearly inverted.
Full adjustment typically takes 5 to 7 days. Most people feel functional within 3 or 4, but sleep can remain slightly off for a full week.
What jet lag feels like on this route
The near-complete inversion means you'll experience both insomnia at night (wide awake at midnight) and severe drowsiness during the day (fighting sleep at 2pm). It's a double hit that can feel quite disorienting for the first couple of days.
Many people experience a "second wind": feeling exhausted at 8pm, fighting through it, then feeling strangely alert by 10pm. This is your London body clock catching its stride. The trick is not to ride that wave but to get into bed anyway.
Appetite disruption is common. Your gut has its own circadian rhythm, and a nine-hour shift throws it off. Eat at local mealtimes even if you're not hungry. It supports the adjustment.
Day-by-day recovery plan
You'll land in the morning, exhausted. Get through immigration, drop your bags, and get outside. Tokyo is an excellent city for walking, so use that. Morning and midday light exposure matters most here. Eat lunch at local time. If you must nap, 20 minutes maximum before 2pm. Take melatonin at 9pm and get into bed even if you're not sleepy. Keep the room dark and cool.
On day one, you'll likely wake between 2 and 4am. Stay in bed with dim light for a while. If you can't sleep after 30 minutes, get up and do something quiet. Get outside again once the sun's up, before 9am if possible. This is the window where morning light pulls your clock forward.
Days two and three: the insomnia should start easing. You might now fall asleep by midnight and wake at 5am. This is progress. Keep up the morning light routine and evening melatonin.
Days four and five: sleep pattern approaching normal. Most people are sleeping 10:30pm to 6:30am by day four or five.
Days six and seven: fully adjusted.
What helps
Morning light between 6am and 10am is the most effective intervention. Tokyo mornings are bright, so use them. Walk to breakfast, explore a temple, sit in a park. This accelerates the clock shift by up to an hour per day.
Avoid bright light in the evening, particularly the blue-white fluorescent light in Japanese convenience stores and train stations. This tells your brain it's still daytime. If you're out in the evening, sunglasses help.
Melatonin (0.5 to 1mg) at 9 to 10pm local time for the first 4 to 5 nights.
Japanese food timing works in your favour. Traditional meals are served at consistent times and tend to be lighter in the evening, which naturally supports circadian adjustment.
What to avoid
Don't go to sleep at 6pm on arrival day. You'll wake at midnight with a full night ahead of you and no light to fix it.
Don't spend your first day indoors. Hotel rooms and museums are dark environments that give your brain no clock signal.
Don't use caffeine after noon for the first few days. You need to be able to fall asleep in the evening, and caffeine has a 6-hour half-life.
The return trip
Coming home (westbound, Tokyo to London), you're delaying your clock by nine hours. This is easier than the outbound because delay is more natural. You'll experience early morning waking (3 to 4am UK time) for a few days, but daytime functioning is usually fine. Expect 4 to 5 days for a full adjustment.