Two methofs have worked for me.
(i) slash, burn, and mow, and keep mowing.
(ii) use of glyphosate at between 10 and 100 times recommended strength sprayed on to newly sprouting stuff.
This generally kills it stone dead, but don't mess around with 'recommended' strength.
And wera protective clothing and keep pets away and shwoer immediately afterwards etc tec.
Glyphosate.
Not if you use glyphosate it won't. The whole are will be bramble free (and everything else free too).
Just reseed with meadow mix or pasture mix or let nature take its course.
Go to a builders merchants.
Another option is to hire a digger, and dig the bastards up.
Then use the blade to regrade.
Or rotovate.
Seripusly, don'y mess around. Use drastic tactics. Nazi style 'final solutions' are required for proper 'ethnic cleansing'
If chemsitry bother you, use digger to buldoze to ground level, and a ride on mower with (essentially disposable blade in year one) to mulch anything left to silage, and then keep mowing - high setting is fine for pasture - at least once every couple of months. Eventually the bastarads give up, but they will always re-seed, which is why biannual mowing of pasture is de rigeur. Thistles and brambles and hawthorn seeds come on on the wind and in birdshit.