An aquatic solution

For years I fought a losing battle against the persistent and pernicious weeds which invaded the back my garden from the railway embankment. I decided that if I built a pond, then they would have no place to take root.
My father built a concrete pond and it seemed to give him a great deal of pleasure maintaining and developing it.
I went to the library and read up on it. Basically, you dig a big hole, line it with thick fabric and place a pond liner over that, anchor it with some crazy paving and fill it with water.
In practise, it's rather more complicated than that. I marked out the optimum minimum area for a viable pond, 6 square metres, and excavated about a ton of earth, piled up at the back, creating a hole roughly similar to a mirror dinghy. Then I got the linings and paving and filled it with water. There was a shelf around most of the edge for plants in aquatic containers and a sloping 'beach' at one end for wildlife to use and a sharp drop the other end for a waterfall. All this effort gave me an abdominal  hernia, which required an operation.
I bought two preformed cascades and installed them, along with a pump and filter, which also involved installing outdoor electricity. Both pump and filter turned out to be inadequate, to I had to invest in bigger stuff.
I populated the pond with marginal and oxygenating plants and bought some fish to eat mosquito larvae.
All seemed well until I was about to go away to house sit for my sister. The pump broke down and had to be replaced. While I was away, my neighbou,r who was charged with keeping an eye on it, sent me a message to say that all was not well. I cut short my holiday and returned to find the pond half empty and the fish gasping for breath. The filter had clogged up and water was not flowing. Just 10 days of hot rainless weather had evapourated half of the water!
I had to install an outside tap and run a hose to a ball valve to keep the pond automatically topped up.
Then came the heron. It seemed that all the fish had been eaten. I restocked the pond with fish and installed all sorts of seemingly clever devices to deter this menace, to no avail. This old heron had seen them all before and was not to be deterred.
Then one day there was a truly remarkable encounter. I had surrounded the pond with fishing line, installed a decoy plastic male heron, placed a net over the pond, supported by wooden laths and a passive infrared sensor which sprayed a jet of water at anything warm blooded which moved before it. The heron arrived, cautiously. It stepped over the fishing line, kicked over the fake heron and approached the sensor, very slowly. It responded but the bird merely got splashed on the beak. There is an 8 second pause before it fires again, giving the bird time to move directly in front of it. It only responds to movement across its range. The heron casually walked along the wooden lath to the centre of the pond and peered down. There was plenty of duckweed under which the wary fish could hide and a net to trap the heron's beak if it made a stab. After a while, it turned its head towards me. It knew I had been watching it. The message was, 'Ok, you you've got me buggered here!'
It never returned, but the scared fish came out of cover, so I had too many of them, and they were breeding too. This played havoc with the filter, so I had to get a really big one.
I had misinterpreted the heron's message. What it was trying to say was that it was here to keep the fish population under control and get a meal in return for my services, you idiot!
I didn't need the fish to control the mosquito lavae. Damselfly larvae would take care of that, given the chance.
Nonetheless the pond has rid the area of brambles, thistles and suchlike and is a pleasant place to sit and listen to test match special and grow watercress. Furthermore, now that there is a hosepipe ban in place, I am exempt, on account of having a pond with fish!