For the tomato ketchup, place the vinegar, bay leaf, spices and sugar in a heavy-based pan and bring to a simmer.
Add the remaining ingredients and bring to the boil, stirring to prevent any sticking.
Reduce the temperature and simmer, stirring frequently for 30 minutes - be careful the mix doesn’t catch and burn.
Blend in a food processor or liquidizer and strain the sauce through a sieve.
If you find the sauce too thin once cold, then simply re-boil and thicken with a little cornflour mixed to a paste with water, being careful not to make it to starchy and too thick. This will prevent the tomato water separating from the sauce.
Heat a deep fat fryer to 170C/350F (CAUTION: hot oil can be dangerous. Do not leave unattended).
Place the potatoes into the fat fryer in batches and cook for 2-3 minutes until just tender but not coloured.
Drain onto kitchen paper and turn up the fat fryer to 190C/375F.
Sprinkle the yeast and sugar into a mixing bowl.
Pour over the beer and vinegar and whisk in the flour.and salt
Leave to ferment – it is ready to use when the mixture starts to bubble.
Dip the cod fillets into the batter and fry until golden-brown and cooked through – about 3-4 minutes.
Remove with a slotted spoon and drain on kitchen paper.
Keep warm on a tray in the oven if necessary.
Place the semi cooked chips back into the fat fryer in batches and cook for another 2-3 minutes until golden-brown and crisp.
To serve, pile the chips onto the plate and place the cod alongside. Serve with a dollop of tomato ketchup.