In 18th century London the eel was an abundant, cheap, nutritious and readily available food source from the Thames. Eels became a staple for London's poor, particularly in the East End where cockneys were also abundant.
The favourite eel dish was jellied eel, where the eels would be cooked and then allowed to cool in the cooking broth which would solidify into a jelly as it cooled. I’m sure it tastes as good as it sounds. Other common dishes were hot stewed eel or fried eel with mashed potato.
The first "Eel Pie & Mash Houses" opened in London in the 18th century, and the oldest surviving shop - M Manze - has been open since 1891. Although jellied eels is not as popular today as in the past, it can still be ordered in the few Eel Pie & Mash Houses that remain.
Now you can fully appreciate the subtle genius of The Mighty Boosh as The Hitcher sings his song about eels.