Bp began drillinga relief well not too long ago.
If a relief well was the only viable solution to the problem why would BP have begun drilling one at the beginning of this while simultaneously trying other approaches?

Canada requires relief wells for drilling. BP, as recently as March, protested this regulation there as being an unnecessary aversion to a situtation similar to what we are currently seeing. The reasoning was that all of the safety systems on the rigs should be adequate enough to prevent this type of thing. The overlooked part of this is the human error factor.