For the tomato chutney, heat a frying pan until hot, add the caster sugar and cook for 1-2 minutes, or until the sugar has melted and is pale golden-brown.
Add the chopped tomatoes, vinegar, chilli flakes, apple and thyme and cook for 2-3 minutes. Season, to taste, with salt and freshly ground black pepper.
For the Welsh rarebit, preheat the grill to high.
Heat the cheese and milk in a saucepan, stirring regularly, until the cheese has melted.
Add the flour and breadcrumbs and cook for a further 2-3 minutes stirring continuously.
Remove the pan from the heat and set aside to cool.
Whisk in the Worcestershire sauce, egg, egg yolk and mustard. Season, to taste, with salt and freshly ground black pepper.
Meanwhile, lightly toast the bread on one side. Spread the cheese mixture onto the un-toasted side of the bread and grill for 1-2 minutes, or until the cheese is bubbling and golden-brown. Serve the rarebit hot with the chutney.