Line a 19cm loaf tin with baking parchment and set to one side, on a trivet (unless you have a heatproof worktop).
Put the sugar, cream, milk, butter, salt and liquid glucose in a heavy-bottomed pan that can hold around 3 litres, as the fudge will really bubble up.
Using a wooden spoon stir the mixture over a low heat until the sugar has dissolved and then bring it to a boil, stirring constantly.
Reduce the heat to just below a boil and cook for 8-10 minutes, stir constantly and ensure the mixture reaches 116C.
Take the pan off the heat, wait until it reaches 110C and then add the vanilla extract and the rum. Stir the fudge for 8-10 minutes until the mixture becomes thick, creamy and slightly grainy.
Spoon the fudge into the prepared tin and leave to cool (preferably overnight) before using a sharp knife to cut the fudge into squares.
Store in an airtight container in the fridge and the fudge should last for around a fortnight.