In reply to Al Evans: I have a couple of thoughts on this. Firstly, as Iain says above the two runners GB had today have pbs within 2mins of Ron Hill's then record time but that's well off current race winning times (look at the number of 2.05 times set by Kenyans). So you have to wonder why have some nations managed to improve the standard of their top runners over the last 40years when GB (and indeed lots of Europe) failed in achieving this in their training. Are their training methods that much more effective?
Which inspires my second point, maybe GB training isn't any worse but we aren't getting the potentially quickest athletes becoming long distance runners. Some others may be able to confirm if this is the case, but I get the impression that running used to have a fairly high status amongst the GB populous, but this status doesn't for the most part hold any more compared to a lot of other sports. Excepting a few weeks after things like the Olympics, there will be few kids wanting to be runners rather than footballers or rugby players etc. Those with talent shown early are less likely to be drawn to athletics.
For a lot of African nations, it is the sport, so you'll get a bigger field of talent to search from and less likely to disappear into other sports. Further this means harder competition. You may disagree, these are just my thoughts.