Tomatoes not setting fruit

I have three varieties of tom in the GH this year: Marmande which are doing fine if a bit slowly, Yellow Brandywine and a black type called Carbon are healthy but worrying. The latter two (growing for the first time) have been in heavy flower now for at least a couple of weeks but hardly any fruit is set. I keep the GH doors open for insects and also go around a couple of times a day tapping the plants to generate the pollen. Because the Marmande seems to be behaving, I suspect these other varieties may be problem germinators... or is it just the awful weather?

My feeling is that this will be a common problem this year-you seem to be doing all you can-it is a matter of sun and increasing the humidity-a lot of the flowers on mine have just dropped of or just sat there- it is so soul-destroying-just live in hope-not a lot of comfort I know.

It probably does differ from variety to variety.

Let's blame the lack of sunshine! Only 121kWh registered in June from my solar pv, compared to 195kWh last year, which wasn't that great. I believe that tomatoes need sunshine and heat. It's pretty warm these days, so maybe that will help. If it can be of any comfort, here are my moneymakers a couple of days ago (with the bright courgettes below) still no fruit, but plenty of flowers which have suffered from the recent strong winds:

Thanks for the empathy. Unrelenting gloom ain't it?

Try spraying the flowers with water either in the morning or evening. This helps the fruit to set.

My dad is a great tomato man he told me to tap the flowers in the heat of the day to encourage pollination. He also had a rabbits tail for this job too, but not having a rabbit about I use a cotton bud just very lightly go from flower to flower cross pollinating. I do this for peppers as well it always works

You don't need to cross pollinate. They're self-pollinating. Just give the flowers a tap or a brush with your hand. One of the great frustrations for tom growers is flowers not setting fruit. Over-watering and over-fertilising can be a factor. High temps and humidity can also work against fruit setting. We've had a week in the high 30sC here and flowers are shrivelling and dying.

Well, they love the heat until it comes to setting fruit. That's the only real issue with heat. Humidity, too, for that matter.