Is It Worth it?

I recently broke up with my girlfriend of almost two years. I have always kind of had a thing for her best friend and we have always been exceedingly flirtatious and close like that.

Basically, its been a running joke in the group of friends that if my girlfriend and i ever broke up I'd end up with her best friend. Now that we have, i don't know whether or not to pursue this.

My Ex and i were trying to be friends but i doubt it will work out all that well.

Is it worth possibly ruining a friendship to pursue my Ex girlfriends Best friend who i've Always REALLY liked?