In north west London on a summer Sunday afternoon

 The Welsh Harp reservoir in Brent is like another world - sailboats on a pond -

It was built in the 1830s to supply water to the canals, which were a very important mode of transport for coal and goods before trains took over. In the 1880s the local pub, The Old Welch Harp, was a popular place for day-tripper excursions - it had its own train station and even had a little zoo, from which a bear once escaped - but by the end of the century the area became urbanised and the pub closed in 1903. Whether the reservoir or the pub came first is a subject of controversy.

 The reservoir is on the Capital Ring - "the M25 for pedestrians" - 60 miles of footpaths right round the city -

Going west, 18.5 miles to Richmond Lodge; going east, 24.5 miles to Woolwich Foot Tunnel

Near the reservoir is our favourite garden centre, the one with the big section for fish -

 Photographing fast-moving fish in dim light, with reflections on the glass of the aquarium or the top of the water in the indoor ponds, is no easy matter.

So many different types are available for purchase, common and rare, small and quite large, in gorgeous shapes and colours -

The corals and sponges come at a price too.

Then, for something different - home and into the garden. This mass of undifferentiated greenness, beloved of the local colony of sparrows, is a pyracantha (which sounds more like a snake than a shrub) - vigorous and thorny. It's been growing there for about 30 years, and hasn't been seriously trimmed in the past decade, at least.

So far this year, nibbling away with the secateurs on sunny Sunday afternoons, I've taken out three "green bins" packed full of clippings, even large branches, and have cleared the suckers from the space under it, revealing a long-lost forsythia that used to cascade its yellow blooms gently every spring -

 Much old wood, now barren, is left - and the new shoots are whippy and struggling in the gloom -

not to mention the rogue honeysuckle that is entwined in it, and gives a lovely scent in the late-July evenings.

Apparently pyracanthas' stems aren't all that strong, so the shrub should be kept in check, as it could topple over and bring down the fence, not a happy thought.

The sparrows dart in one after another, perhaps to rest, perhaps to feed, certainly to chirp. If you're watching from inside the house, glancing up from the computer every now and then, just when you've forgotten they're in there, the bush explodes with birds as they leave all together. The number of sparrows in London is steadily declining, and I hope they'll consider this pruning work an improvement and continue to visit us.