Snails will eat them if they are near the ground, I had holes in some from a snail on the wall behind the plants.

To name just a few, birds, rabbits and squirrel will eat your tomatoes and whenever they come across them they considers them a treat.

Thanks, I managed to put the lowest truss in large plastic plantpot eventually and daved all the rest, but I'll watch out for them better next year.
Actually I only set them outside because My greenhouse was full but I'll definitely do it again next year as I get a lot of extra toms 3-5 weeks after the inside ones have gone.