That's why it's raised beds, Dowding's garden is on heavy clay.
When you put a six-inch plus layer of light, friable material on top of clay, it drains well, the water disperses and evaporates, and this is deep enough for the root-zones of many plants.
Worms love it and aerate it, and after a couple of years of adding more mulch manually, will deepen the light soil by breaking into, and incorporating with it, some of the clay soil underneath.
Now, although clay soil is difficult to work, slow to breakdown, cold and wet, it does hold nutrients well, and its inculcation to the bed means that it's, to my mind, the BEST medium upon which to use this method.
My allotment is heavy clay, and my onion & garlic beds are fantastic.
I'd turn the whole lot over to no-dig if I could afford to.