Best weed killer for brambles?

[MissCherryCakeyBun]

Our new garden is smothered in brambles....house empty for 2 years and no gardening for 2 more before that. I'm currently harvesting all the blackberries to make jam and blackberry whiskey and to let the birds have a munch I will leave until the end of the summer before cutting them all back ( I've removed the berryless runners)
When they are done and chopped back what's the best weed killer to use to try and stop regrowth? Digging them out isn't an option due to the quantity and that they are growing right under trees etc.
My OH wants to try a weed flame gun on them but can't see that doing anything to the roots
Has anyone else had a similar issue?

Also any help with bindweed as it's almost as prolific as the bloody brambles

Anyone? Or shall I just get a flame thrower

Watching with interest. I've got the same problem

After harvest cut all the brambles down to ground level and burn/get rid. Wait until they resprout in the spring, and when there is sufficient leaf cover to absorb the poison, spray them with a systemic weed killer which will kill the roots. I would use glyphosate because it does not linger in the soil, but there’s another called SBK which works well. The weak point in this procedure is not waiting for enough leaf cover for the poison to be absorbed. Remember you’ll get more coming from blackberry seeds germinating. Same method works well for bindweed.

You could spray the whole area now, but the brambles need to be actively growing, and it’s hard to get the spray onto all the leaves if it’s an established mess

Thank you so so much, currently to 2 litres of blackberry whiskey on the go and now freezing them so I can make some jam when I have a good quantity. I picked 1kg on Sunday afternoon in 40 minutes.
I will chop them right down when done and then follow your instructions in the spring.
Really appreciate your help

Agree with the advice from Trethew. There are stronger products than SBK that will work but they are only available to farmers or licensed users (e.g. professional gardeners or landscapers)

Key thing is that the plants are growing strongly (i.e. Spring) and that you can wet every leaf with the spray.

Thanks so much beennout chopping the bits down I can and been burning in the garden incinerator ( very care fully obviously)
We don't yet have our green garden bin ( £55 a year here in Somerset and that's not a rolling year either so I've paid it for 8 months but at least it will be available )