Roundup, but even then you will need to dig out the roots of some of the perennial weeds.

Thanks Moon growe

If the area isn't too big you could cut everything down to ground level and then dig, burying each sod a spit deep. I am in the middle of doing that right now with part of my lawn,and apart from aching shoulders its beginning to look ok. The advantage is that this way you are returning the nutrients to the soil and adding humus and slightly improving the soil structure. And you feel so very virtuous when you stand back and look at it! You will have to dig it over anyway to get the perennial weeds out, and not much will survive being buried to that depth (unless you have horsetail or bindweed or other horrors)

Steragram from another post by Pippy she is disabled and this is why I didn't suggest any serious digging. Frankly I couldn't double dig now either!

Oh, I'm sorry Pippy, I didn't realise. Roundup it is then.
I am finding mine quite hard work actually, and taking it a row or two at a time, as I'm now the grand old age of 71 and haven't got as much energy as I had even two or three years ago. Scary, and very frustrating.

Wow Steragram I am impressed I'm only 62 but I do have heart problems, a hole between my two ventricles, so my blood is never fully oxygenated.

That must make you tire very easily - not good if there's digging to do. But fortunately you have an OH who is into gardens - mine will cut the grass and the hedges but I wouldn't let him loose on the plants! I have been tempted to bamboozle him into digging some of the new bed but have managed without so far!

B does all the heavy work in our garden Steragram, though when I was younger I could hold my own! It can be frustrating at times as I want to do more.