cineman wrote:

I am growing runner beans for the first time for quite a few years, have
plenty of flowers, but up to now only one tiny bean has "set".
The atrocious weather this week has slowed growth anyway.

Some of the flowers appear to have been neatly nipped off, or else dropped
off for some reason, and I remember having this frustrating problem on
previous crops, i.e. - losing the first few pods at least.

As cineman said, the simplest explanation is that they dropped off of
their own accord - too cold, not pollinated etc. In which case don't
worry - they'll soon start setting and no doubt you'll have more runner
beans than you know what to do with before you know it!

The leaves have also been eaten away to some extent, but I was only able
to find a tiny black caterpillar on one, and I do use slug pellets when
the weather is damp.

Most likely that will be slugs or snails. I don't find they're a major
problem on runner beans once they get established. The beans should
grow away and the slugs seem to concentrate on the lower leaves and
other plants within easier reach.

If the eaten leaves are higher up, have a close look on the supports
they're growing on - sometimes snails with a head for heights stay up
there in the daytime and eat the newer softer leaves at night. But
picking them off and chucking them away seems to deal with the problem.

Peter