Wood Green, London.
An object which looks like a large boiler or distilling barrel appears on screen. A man wheels a trolley with a basin on and places it under the strange barrel. He opens a tap at the bottom and a glue-like liquid starts pouring into the basin. After the basin is filled, he closes the tap and wheels the basin next to a long working table. He pours the liquid across the table helped by another man.
This is a sweet factory in Wood Green where London Rock is made. Glue-like liquid is toffee of which the London Rock is made - a mixture of glucose and cane sugar boiled in the strange barrel at 260 degrees Fahrenheit.
A man pours a colouring into the toffee and starts mixing it slowly. C/U shot of the man's hand mixing colour into toffee. M/S of the two men making letters. The man wearing glasses is Mr Jerry Toll who has made the rock for 38 years. He and another man (young, possibly apprentice) are mixing strips of red and white toffee into rolls, each containing an individual letter. Rolls with individual letters are then placed into a large roll (a huge one) which, when stretched and cut, becomes London rock.
Three men are lifting a huge roll to chain it on one side so they can hang it to stretch. After the roll is stretched, hand rolling takes place. Rolling has to be done very fast since it takes an hour for the toffee mixture to become too hard to handle. Succession of shots showing how huge thick roll is stretched and rolled into thin strips of London Rock. Rock is then measured and cut (with large scissors) into strips seven inches long ready for packaging.
Film ends with a great C/U shot of a pile of circles, each reading 'London Rock'. No wonder they are famous!