You can't fly if you run out of batteries!
You may be asked to turn on any electronic or battery powered device at the airport checking points (this means telephones, tablets, e-books and laptops), you may have to do this in front of security staff.
If you are unable to demonstrate that your device has power you will not be allowed to fly on your planned flight. This means that along with checking for passport, tickets and wallet before you leave home you also need to check items are fully powered and working.
Taking broken devices in your hand luggage to the airport will also mean you wont be allowed to fly.
I foresee a particular problem for passengers flying to the US as transfer customers, especially those on long journeys. If they deplete power in their devices while on the first part of their journey, they could hit problems during checks while transferring at Heathrow.
We all know that there are very few charging sockets at airports!
I'm told that Heathrow started to do new checks yesterday - which involve "various routes" (not just the USA).
BA tells us that so far no passenger has been denied entry to a flight.
Virgin tell us they started the new checks yesterday and so far no passenger has been prevented from boarding.
Manchester Airport says it hasn't changed anything since the tighter rules came in last week.