The airport which is the main target of the Government’s ban on electronic devices has a security flaw that renders rigorous checks futile, The Independent can reveal.

After clearing six separate security hurdles at Istanbul airport, passengers bound for London Heathrow mingled in the gate area with newly arrived travellers who had faced no extra checks, The Independent has discovered.

Starting at the weekend, the Department for Transport made it mandatory for airlines flying from Turkey, Egypt, Saudi Arabia, Jordan, Lebanon and Tunisia to the UK to remove laptop computers, tablets and e-readers from passengers' cabin baggage. They must be transported in the hold.

Simon Calder reports from Istanbul airport on new ban on electronic devices in hand luggage for specific UK-bound flights

Professor Anthony Glees, director of the centre for security and intelligence studies at the University of Buckingham, told The Independent the ban “defies logic.”

“If security is lax in any airports - which we know it to be in some more than others - then the answer is not to let anybody take anything electronic, not simply to single out laptops,” he said.

“If you are going to keep your house safe you have got to lock it up, you cannot lock it up sometimes and sometimes not.

“Terrorists will always go for the weakest link in the chain and this demonstrates a non existent link in Istanbul, which means that the idea that this policy makes sense is thrown into the wastepaper basket.”

The ban is based on intelligence suggesting an al-Qaeda plot to bring down an aircraft with explosives concealed in consumer electronics.

The airport most affected by the British ban, in terms of passenger numbers, is Istanbul Ataturk. It is the hub for Turkish Airlines, which has up to six flights a day to Heathrow, as well as two daily departures to Manchester, 10 a week to Birmingham and five a week to Edinburgh.

British Airways also flies from Istanbul to Heathrow, while AtlasGlobal flies from the airport to Stansted.

In total, around 2,500 people fly from Istanbul to the UK in a typical day.

"If there is specific intelligence then the ban is justified - but in that case the airport should have been boycotted altogether. You cannot be half in and half out, half locked and half unlocked," Professor Glees said.

"Everybody has an interest in making airport security as good as it possibly can be and Turkish airports cannot be a weak link because we are all interconnected."

Istanbul airport already has heightened security following a terrorist attack in June 2016 in which more than 40 passengers and staff were killed by gunmen. Vehicles entering the airport area are searched, and all passengers face additional screening before they reach check in.

Passengers for the UK are now checked in at a separate area alongside flights to Israel. Besides the standard screening to go “airside”, three extra security hurdles have been added. The last, at the entrance to the departure gate, is a thorough hand search of cabin baggage. Any device bigger than a standard smartphone is confiscated and put in a special sealed case which is then opened on arrival at Heathrow.

Passengers on flight TK1983 on Saturday evening seemed resigned to increased security. Lesley Abdela from East Sussex said: “It’s just added to the stresses of travel. Travel’s not a pleasure any more.”

Gary Mackay, who was in transit from the Seychelles via Istanbul on a journey home to London, said: “They’re doing a thorough job. I’ve got no complaints whatsoever.”

His wife, Anid, said they had learned about the new rules while on holiday, but said the restrictions could come as a shock to some travellers: “If you were somewhere like the Seychelles and you weren’t checking the news on a regular basis, you would have missed it.”

But as the heavily screened travellers were waiting to board the Heathrow flight at Gate 202, an entire planeload of arriving passengers wandered through what was supposed to be a security-sterile area.

It was an alarming example of a failure to look at the bigger security picture. I watched while security staff diligently discovered and removed PlayStations and Kindles from travellers heading for Heathrow – yet no one noticed that 100-plus passengers, who had not been screened for devices, were mingling in the gate lounge.

Philip Baum, editor of Aviation Security International magazine, said it was a fundamental flaw that made a mockery of the new rules. “There is no value in restricting people carrying laptops through checkpoints if they can be given them, or other items, just prior to boarding,” he said.

The Independent reported the breach to Turkish Airlines and the UK Department for Transport.

Many aviation figures have questioned the value of the UK ban, which is a variant of similar rules imposed earlier by the US. Anyone seeking to take large electronic devices in the aircraft cabin from Istanbul to Britain needs only fly to Amsterdam, Paris or any of dozens of other airports and change there for an onward flight to the UK.

Airlines affected by the ban are likely to suffer financially. Mr Mackay said: “We’ll choose a different airline and a different route next time.”

Business travellers choosing flights affected by the ban will be required to check in earlier than normal. They will be unable to work on their laptops on board. And if they are accustomed to travelling with cabin baggage only, they will need to wait for checked luggage to arrive on the baggage carousel on arrival.