Seek and ye shall find. Common Bistort (Persicaria bistorta) doesn't seem to be all that common in my experience. I have rarely seen it in its natural habitats: moist meadows and boggy wetlands.
 And yet today I saw a fine stand of Bistort in my home town of Hitchin, Hertfordshire. The Purwell Meadows are surrounded by post-war housing estates but retain the flora and fauna of a different age. Rather like the Wild Clary I mentioned recently [14th. May] the presence of P. bistorta  has somehow escaped my attention despite being familiar with this locale since childhood.
 I suppose I haven't ever passed by when it's in bloom because the tall spikes of pink flowers are hard to miss.