Combine 1 lb 7 oz/650 g of the glucose syrup, the granulated sugar, and water, in a heavy-bottomed saucepan and stir to ensure all the sugar is moistened. Bring to a boil over high heat, stirring to dissolve the sugar. When the syrup reaches a boil, stop stirring and skim the surface to remove any impurities. Continue to cook without stirring, occasionally washing down t