In a large non-aluminium saucepan, combine the plum tomato, celery, onion, sultanas, brown sugar, vinegar, ginger, chilli, allspice and salt. Bring to the boil. Simmer, uncovered, stirring occasionally, until ingredients are tender and most of the liquid has evaporated, 20 to 25 minutes.
Remove pan from heat. Stir in grape or cherry tomatoes. Let cool to room temperature. Transfer to a covered dish and refrigerate for at least 24 hours. This will keep for up to 1 week.