Although we had previously drained the pond by removing the plastic liner, every time it rained the pond filled up again due to its clay base. About fifty million wheelbarrow-loads later, we were down to the soil.
The dogs were distraught to bid farewell to their alfresco swimming pool. You can almost see Penny's teeny tiny brain in action: "Noooo.... my beloved pond has all but disappeared... oh, wait... maybe I miraculously quadrupled in size! Yes! That must be it! I am The World's Most Giant Jack Russell!". Bless Princess Penelope. There's plenty of prettiness, but not much brain.
We ordered a tonne each of topsoil, forest bark and river gravel. We used river gravel because the pebbles are a variety of sizes (therefore providing better drainage) and also because our garden has acidic soil (hello, rhododendrons and camellias) and most gravel is limestone based which could disrupt the natural balance of the ground.
We shovelled all the gravel into the bottom of the pond, and then alternated layers of forest bark and soil, ending with a layer of forest bark in order to avoid removing a swimming pool and creating a mud bath. It isn't quite level with the surrounding grass, but that's OK - we plan to level the whole of this part of the garden and turf it over to make a mini football pitch for the girls, so in due course we'll take some soil from elsewhere and use that to level the pond area.
I'm happy to report that this method worked flawlessly. We no longer have a pond, not even the merest smidge of a pond. Well, unless of course you count the numerous giant lakes that have sprung up elsewhere in the garden. Guess all that famous Manchester rainwater has to gather somewhere. The dogs are in alfresco swimming heaven. Waah!