Thank you everyone for your excellent advice. What is annoying is this is a new raised bed garden built up with soil from the local garden centre. They had 3 soil blends and I bought a mix of all three. And the plant was bought at a hardware store. It has taught me that purchased soil is not always safe. I suspect it was mined soil bereft of good biology so I added good amounts of manure and mulched with sugar cane mulch. I hope the other tomatoes in the bed stay safe. The bed also has chilli, basil, thyme, beans, yakon, sage, eggplant and peanuts. If they survive I’ll rest it with cabbage in winter and sweet potato next year.