Well today my dad and brother finally got around to helping me sort it out properly.
What we removed from the swamp (most quantities estimates):
- Nearly a mile of marsh marigold stems
- Two or three pounds of dead leaves
- Two golf balls
- An entire rockery
- One inexplicable Christmas-tree bauble which certainly never belonged to us
- Four or five pounds of moss
- At least twelve pounds of silty roots and unidentifiable things
- About twenty litres of primordial ooze
What is left in the pond:
- Two marsh marigolds
- About ten yards of pondweed
- Enough silt to cover the bottom of the liner
- A couple of dozen tadpoles
- A few snails
- Two swamp beasts (to the uninitiated, they would appear to be mere frogs, but we know better)
So we have tamed the swamp, but I doubt that it will take very long for it to be well-covered with a thick growth of weed, and by next year it will probably be well on its way to being thoroughly choked again.
I also tried to tame our resident triffid (which to the inexperienced eye would seem to be no more than a large and unruly rosebush), but gave up when it bit me painfully in the thumb.