It is not always the case that runway direction is all one way, or all the other. Here at London City it is common that sometimes crews will request a departure in the opposite direction to the standard in use; there are a range of issues that can lead to this (the "performance reasons" request described above), from the aircraft being marginal in performance in the opposite direction due to weight and temperature (the main issue being obstacle clearance minimas on climbout), through to just wanting a shorter route.
It is very dependent on there being no inbounds nearby, and the aircraft still being within any headwind limits, so a still summer day is most likely, but if they can be accomodated it will happen.