Tennis player Jamie Murray - the brother of British number one Andy Murray - was caught up in the queues at passport control on Thursday night.
He tweeted these pictures, estimating that there must be a couple of thousand people waiting in line.
He added the hashtag #thirdrunwayanyone?
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The mayor claimed last week the bridge would cost more to cancel than to build. He said £37.7m of public money had already been spent.
The houseboat in Chelsea, west London, comes complete with three bedrooms, three bathrooms, a reception room and its own patio.
The city is one of a small number which has seen an increase in traces of the Class A substance over recent years.