The Head of the Border Force, Brian Moore, said that our border controls were generally very efficient.
The Border Force expects most British or European nationals to travel through passport control in 25 minutes or less, and most foreign nationals within 45 minutes.
But occasionally, disruption is caused by issues like flight bunching, where several flights arrive at the same time.
He added: "Occasionally there is some disruption to travelling passengers, which we regret. But we all want a safe United Kingdom and a strong border."
More top news
One of the teenagers was left so badly burnt doctors say he may lose his eyesight.
Jame Murray's challenge is to deliver Mr Khan's manifesto pledge to build more than 50,000 new homes a year - half of them affordable.
Ryan Lee was removed from the finishers' list because he was not picked up by the 5k checkpoint.