Britons should pay close attention to a little-known airport regulation that could result in your mobile phone or laptop being confiscated before you've even set foot on your flight.

The rule is enforced at airport security and has been known to catch out passengers travelling with the likes of TUI, British Airways, Ryanair, or easyJet, and others. It's worth noting the restriction is enforced at airports, rather than a rule from the airline themselves.

Most travellers carry at least one electronic device in their luggage, whether it be a mobile phone, tablet, or laptop, and yours will undoubtedly store your boarding pass and perhaps a Netflix series or two to enjoy en route. However, should you reach airport security only to discover your battery is at 0%, you could find yourself in serious difficulty. All electronic devices must be capable of powering up, as security personnel are permitted to request that you switch them on, reports the Mirror.

Should a flat battery prevent you from doing so, you may be denied boarding, or face the difficult decision of abandoning your device altogether. The UK government's official website, which provides comprehensive travel guidance and updates, states: "Make sure your electronic devices are charged before you travel. If your device does not switch on when requested, you will not be allowed to take it onto the aircraft."

Should you make the error of carrying an uncharged device in your hand luggage, your options will vary depending on the airport of departure and your airline. If you've not yet checked your bag, you can place the device inside it, where it will subsequently travel in the hold.

We take a look at some of the major airlines' own guidance on gadgets onboard...

The guidance from British Airways' (BA) website is unambiguous. "Please ensure that any items in your hand baggage are fully charged and switched on before you arrive at the airport. If your device is not charged, please place it in your checked baggage."

They also recommend: "If you are connecting, make sure that you do not deplete power in your devices during the first part of your journey as charging points at airports might be very limited and you may need an adapter."

For London-Heathrow travellers, BA states those with depleted batteries may be required to rebook onto a subsequent flight to allow charging time, though "a fee might apply". Alternatively passengers can deposit items at Bagport, the lost property facility, and obtain a reference number for their belongings. Upon reaching their destination, they can contact Bagport to arrange collection of their property.

Meanwhile TUI has cautioned passengers: "If you're carrying any electronic devices in your hand luggage that are capable of holding a charge, you'll need to make sure they're fully charged when you go through airport security. This is part of new security measures that have been introduced by airports in the UK and abroad. We recommend you keep things like mobile phones switched on until you board the plane, as there might be more checks at the departure gate."

A flat battery isn't the only potential problem. Both easyJet and Jet2 maintain lists of forbidden items which include damaged batteries - so inspect your devices before you even depart for the airport. Jet2's website makes it abundantly clear: "Damaged Personal Electronic Devices (PEDs) and/or spare/loose lithium batteries/cells (including power banks) are forbidden from carriage in all circumstances."

Ryanair offers no further advice beyond ensuring your phone remains charged. Under the FAQ 'What happens if my smartphone or tablet dies before airport security?', it explains: "If you have already checked in online and your smartphone or tablet dies, you will receive a free of charge boarding pass at the airport." Nevertheless, it fails to clarify what alternatives would be available should security decline to permit you through.

Further information about airport security can be accessed on gov.uk.

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