"the escape of an eel from an eel-man's barrow"
are elongated fish, numbering approximately 800 species.
Traditionally, eels were fished from the River Thames where they were plentiful; they were served in an inexpensive dish known as jellied eels.
Jellied eels are prepared by boiling eels in a spiced stock which becomes gelatinous on cooling; they may then be eaten hot or cold.
The dish was often served in special eating places known as Eel, Pie and Mash Houses
, which were common in certain parts of London up until the Second World War. A few still operate today.