Originally Posted by corporate-wage-slave

I personally wouldn't bother on 3 hours, 4 hours plus I may think about it (though even then I'd probably stick to T3, and that is from someone who knows LHR quite well). However on the passport point, the main reason for using the the EU passport in London is that you have the legal right of entry on an EEA passport, which you do not have on a USA passport. You can be denied entry for a long. long list of reasons and at which point this could give (in dire circumstances) a life long hold up entering any part of Europe, not just Schengen (which the UK is not in anyway). If you are an EEA citizen then you can simply use the machines and be landside in seconds, as is your right under the Lisbon Treaty and the underlying concept of European citizenship. If you use the staffed desks on a non EEA passport then the UK Border Force officers have a wide discretion to deny entry, plus you get a much longer queue.