David WE Roberts wrote:
In my back garden the 'soldiers' grown from last year's fallen
tomatoes are starting to ripen fruit.

From this I presume that they in turn could drop fruit to provide
seed for next year.

So what is there to stop tomatoes becoming naturalised in the UK?
I assume that the current climate is conducive to outdoor tomatoes
and the last winter was certainly pretty harsh.

Although I haven't seen tomatoes growing as weeds in mediteranean
areas.
They're listed as escapes in the field guides, so they must appear quite
often. This is SRH's territory, but I'd say the climate here isn't
reliably clement enough to guarantee them regular ripening, or reliable
germination the spring after that.

As luck would have it, I found two feral specimens only yesterday in
the shrubbery at our Friends' Meeting House. These ones were far too
small to have any chance of fruiting before the frosts, but I don't know
how they would have done in a warmer spring than this year's.

They're rather disease-prone, and also rather hungry and thirsty plants
which probably aren't good competitors. And they're separated by many
generations from the wild forms which might stand a better chance.

--
Mike.