21. Newflame briquettes, manufactured by Maxibrite Limited at Llantrisant, Mid Glamorgan, which—
(a)comprise anthracite (as to approximately 75 per cent. of the total weight), petroleum coke (as to approximately 21 per cent. of the total weight) and starch with a catalyst as binder (as to the remaining weight);
(b)were manufactured from those constituents by a process involving roll-pressing and heat treatment at about 250°C;
(c)are unmarked pillow-shaped briquettes and have an average weight of 78 grammes; and
(d)have a sulphur content not exceeding 2 per cent. of the total weight.