Doing some Matrix searches I see that some of the cheap fares start at a EU location and fly via LHR then fly LHR - SIN yet the cost of just starting at LHR is higher. That seems silly... what is happening there? To get these cheaper flights I'd have to fly LHR to the EU city only to fly back again! Seems potty!

Edit: It seems all of the cheaper fares are via LHR... not surprising given it is BA but I am curious how they do the flights so much cheaper starting out in the EU given that there are extra sectors involved.