I heartily agree that it'd be nice to have a forum for questions regarding the laws (and practices) relating to marriage, but then I'm the publisher of the definitive guide to the marriage laws and practices of England and Wales from 1600 onwards, aimed squarely at the kind of questions genealogists come across, so I'm utterly biased!
Adamb - it's not at all uncommon to find examples of bigamy before the early 1970s, when divorce was harder, rarer, and more socially unacceptable than today, but one point I'd note is that such people were nevertheless prepared to marry illegally rather than openly cohabit (in the current sense of the word) - bigamy has today become a rare crime, as nobody turns a hair at a couple living together unmarried. I assume that what you mean by "common law marriages" in your ancestry are examples of couples living together in a stable and enduring relationship out of wedlock? Do you know for sure that this was the case, or is this an assumption based upon not having found a marriage? Have you perhaps found that one was already married to a third party (and was presumably unwilling to commit bigamy)?
As to watercress sellers and prostitution - as a suggestion, you might like to try searching online full text historic databases such as Eighteenth Century Collections Online, or The Times Online for examples of the use of the phrase. I know Professor Probert hasn't come across this phrase in all her research. An interesting observation here might be that Victorian and early C20th middle class writers and journalists were very quick to portray the working classes as living depraved and immoral lives: Henry Mayhew, for example, is always quoted these days as having discovered that more than 90% of London's Victorian street costermongers lived together unmarried. In fact, he was thoroughly condemned almost straight away by a public meeting of London street-sellers, who were outraged at what they called "a downright falsehood", and who pointed out that Mayhew had paid his (very disreputable, and in fact drunken) informants to tell him what he wanted to hear. They challenged him to appear at a meeting to substantiate his claims, but he refused to attend. Yes, prostitution was rife, but being a prostitute by necessity at times in one's life didn't equate to not being married, which was the norm throughout the period.
Liam
