Keep the faith, this beastie is one of natures finest, but with all living things it tends to go away if you keep hitting it.
Kurtail, has an effect like acid but it keeps coming back, concentrated vinegar, as in chip shop vinegar sprayed on mixed with sticky soap, has same effect.
Hoeing and snapping off the emerging shoots stops its sun light supply and it tends to go elsewhere to get light.
With the chemical options, the best results are obtained if you break the outer skin of the plant ie. if you walk over it or scuff it before spraying.
Also, if you can spread vast amounts of lime over the plot and dig or rotaviate it in and then repeat over the season.
But nature will fight back, this plant is as adapted to its surroundings as anyother of natures survivors.
Digmore