[lettie]

There is a slightly more scientific reason for the 2 to the loo thing. Assuming that both women went to the pub at the same time and drunk equal volumes of fluids. The normal adult bladder has roughly a 300 ml capacity. If both are youngish adult females with normal renal, parasympathetic and sympathetic nerve functions, normal sphincter and detrusor muscle action, then they will simply need to pee at the same time. Once you've broken the seal (so to speak) in a pub, you are pretty much garanteed to need to go every 15-30 minutes thereafter, and will probably be in sync for the rest of the night..