There was a good point on that in the Guardian's coverage of the Tour de France - basically it claimed that whilst the rest of the cycling world was engaged in an ever-escalating arms race of drug cheating, the British looked at all the legal ways that you could improve performance (especially in terms of coaching, lets face it Brailsford is one of the greatest coaches ever in the sport), added them all together, invested a lot of money in infrastructure and development of talent and kept trying to improve.
Once the UCI clamped down* on the drug cheats it meant that the British ended up being miles ahead of everyone else.
* albeit not very hard