Having to deal with heavy clay soil I have used the Lasagna method to great success but found that the turf must be stripped off. Not doing so and covering with cardboard or membrane will commit you to cover it with a layer of mulch of a significant depth to allow for root growth and this can be back breaking work too if you find yourself not to have the strength and perseverance you once had.

I came from a heavy clay area too the lawns were badly infested with root tapping perennial weeds. Anyway I dug probably 250 bags of organic compost into it I would find the clay would eventually work it's way back to the surface so it was an ongoing battle. I am intrigued by Charles dowding methods and I think I will try one area to start as my lawns are naturally crisscrossed by narrow concrete paths and a shingle driveway. So I can just try a section at a time. There is ground elder creeping in near the road I wonder how the no dig will cope with that I don't know. The soil here is green sand little bit of clay and lots of stones so it's very free draining and I will need a few tons of organic mulching to keep the moisture in as I got little natural shade no trees.

Good luck with that Alistaire

In my experience, no-dig only works for shallow-rooted plants, which is why it works so well for vegetables which are only grown as annuals. For deeper-rooted plants, such as shrubs and perennials, it pays to prepare the soil thoroughly. I double dug every border in my garden before planting except for one - after five years, the plants in it were just not thriving so I had to remove them all, double dig it, and put them back in. They were then much happier and grew much stronger

I take on board what you day Andrew but I'm lazy and will follow anything that promises me a easy life so I will give it a try . I did once make a raised small border surrounded it with logs so it would have been about 9 deep and filled it with compost over the lawn below and it worked out well although now I think about it nothing that I put in there was particularly deep rooted none of my plants are. The main drawback of Charles system is he works on raised borders that are totally isolated from everything so quite easy to block out light. nothing like neighbours picket fences and open verges just separated by holy bushes these will be impossible to seal off and he told me yesterday his system will only work if an area is completely sealed off no gaps. If any light gets in it ruins getting rid of ground elder for sure. But he did show in his latest bid how to repair gaps where light has got on so not all doomed bit not at all easy where I live . Don't think I would ever seal of my areas from ground elder as it's all underneath the hedges impossible to block out.

Raised borders is the way forward I think scaffold board is great but only lasts about 5 years maybe some protection on them will extend their life a bit further but they go pretty quickly but look the best cheap to buy and deep and will stop a certain about of run off and also stop the creepy enemy a bit.