Until the mid 19th century Barking was a major fishing port where there were plenty of smacks on which to be an apprentice.
Wikipedia says: By 1850 there some 220 smacks, employing some 1,370 men and boys. The boats were typically 75 feet (23 m) long carrying up to 50 tons.
Where there are free-spending sailors you are also going to find flash girls like The Belle Of Barking Creek
Has anyone had any luck locating the Tars Of Blanch tune?