Check your bags are the right size, your liquids are under 100ml and you're not carrying anything sharp or dangerous.
The UK and US governments have changed the rules on people coming into their countries from Turkey, Lebanon, Egypt, Tunisia and Saudi Arabia. You can find out about these changes from your airline. This doesn't affect anyone leaving the UK.
To protect everyone on board, we can sometimes use body scanners.Find out more about body scanners
If you can't turn your devices on, you may not be able to take them on board. You can charge them for free at various points around the airport as well as in Dixon Travel stores.