There have been problems at passport control recently (something to do with a load of lay-offs to save money then oops, not enough people to do the job properly). Anyhow, the government are desperate that we don't look like disorganised numpties in front of the entire world (cos of the expected influx of visitors for the olympics) so they're sort of fixing it (although not by spending money - go figure). Depending on whose figures you believe, maximum wait times are anywhere from 1.5 hours to 3 hours, but that is worst case scenario, and lots of people are saying that they came straight through. In any case by the time you come over, the measures put in place to resolve this little hiccup should be working properly.
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