Lucy Scott-Moncrieff has created an eco swimming pool in her back garden

�To make a pond big enough for swimming is a bold move for a London gardener – one that would often mean having no dry land left. To get round this drawback, human rights lawyer Lucy Scott-Moncrieff had first to buy the flat next door. With her already fair sized south-facing garden thus doubled in width, she had the pond dug right across what had been the dividing boundary. Now it is the main attraction of the space, clear and open enough to reflect a good bit of sky and well placed to be as warm as possible.

As a wild swimmer, Lucy did not want an ordinary swimming pool but one to be shared with newts, frogs, ducks, water lilies, etc. Jumping in is easy, but getting out again can be one of the challenges of wild swimming. Lucy’s pond is well-tamed in this respect, with steps leading down from a flat bridge into a deeper, central channel. The edges are shallower and wildlife friendly, with bulrushes, yellow flags, rush, watercress, mint and marsh marigolds growing around the margins.

The water circulates and gets filtered through a system of pipes, remaining clear and free of duck or blanket weed. “If there is any blanket weed, I chuck it out while I’m swimming. I just have to make sure I don’t go into work draped in green,” she says.

As it happens, Lucy, or her image, does appear in green but in the form of a bronze bust rising above the surface of the pond, occupying the sort of position some might give to a copper sprite or a stone Buddha.

Lucy is dismissive about this bust – her mother wanted it made and kept it. When her mother needed to move, Lucy hoped the bust could be forgotten but her sons were all for saving it. Then it was put in the pond. A head and shoulders emerging from the water is an unusual sight but the bust itself looks calm, pensive, quite at home.

Lucy gets her love of gardening from her mother. She likes a blaze of colour and, to mix things up a bit, rhubarb and fruit bushes in the flower beds, climbing rose in the apple tree, nothing too subtle or too tidy either. She wanted to open the garden for the Yellow Book for the reason many people give – the galvanising effect of a deadline. Getting everything looking as good as possible for a certain date means you can then go on enjoying it for a long time afterwards.

The garden of the second flat came with an old wisteria twisting up an iron spiral staircase and over the conservatory that, despite its big flowering lemon tree, Lucy’s sons see as a poker den. Last year, a nearby ceanothus was flowering at the same time as the wisteria. Seeing their colours together convinced Lucy that May would be the month to open the garden to visitors.

That decision having been made, the ceanothus died. Its young replacement is doing well but can’t yet be expected to produce the same expanse of blue. Still, so much else was budding up at the time of my visit (roses, magnolia, crinodendron, herbaceous perennials) there will be no lack of colour. There are three wisterias altogether, two mauve and one white, and quantities of plants in pots, ready to be transplanted into the borders. What exactly visitors will see in mid-May must depend on the weather.But the pond on its own is worth a visit – even though the National Gardens Scheme insurance policy has put an end to Lucy’s hope of offering visitors a swim.

Lucy Scott-Moncrieff’s garden at 27 Nassington Road, NW3, is open on Sunday May 13 from 2pm to 5pm. Teas, light refreshments and wine