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The BBC's transport correspondent has told the BBC's News at One programme that although the attack started before the security checks - like the Brussels attack in March - it might be counter-productive to bring the checks closer to the front doors of airports.

He said: "You might think, well OK, let's move these checks further away from the airports, that does happen in some countries around the world.

"They did that in the 1980s at Heathrow after the Lockerbie bomb. I spoke to the man behind that and he said it made the problem worse, because actually you have a big gathering of people away from the airport, on pavements, and they're just as vulnerable if not more vulnerable than they are inside the airport.

"Really the way you stop these things is through intelligence, through finding out they're going to happen in advance.

"You can also train more staff to look out for suspicious circumstances and you can have face recognition on CCTV but there is a limit to what you can do."