~ Posted by Robert Butler, July 30th 2013

The hottest July in Britain in seven years has just come to a rapid and thundery close. On the way into work, I crossed St James's Park and T-shirts and flip-flops have given way to kagouls and £5 Union Jack umbrellas. Weeks ago, a yellow-green algae had carpeted the lake and the park manager had put up a sign to reassure visitors.

The weed is not harmful, the waterfowl find nutrients in it, and it is an indication of water clarity.

Almost overnight, the algae has shrunk back to a quarter of its size. It wasn't this morning's only surprise. Fourteen million tourists visit London each year and all summer there has been a solid crowd taking photos on the park's bridge—Buckingham Palace offers a backdrop in one direction, the London Eye in the other. That crowd had melted away as dramatically as the algae. The sky was back to a milky-grey and the dripping trees were a darker shade of green; but the most striking change—after this unusually hot July—was not a visual one.

From the damp seats on the tube train to the wet grass and blackened soil in the park, the rain has released a bunch of fresh smells. Everything felt a little bit livelier. In our series "What is the best smell?", writers trumpeted the charms of the wild rose, new-mown hay, baked bread, frying bacon and Indian railway stations. But the poet Robin Robertson went furthest by suggesting that the best smell was rain itself. In our online poll, readers agreed with him. Robertson wrote that rain is "no smell at all but only a washing-away, a cleanness and yet another chance to start again." This morning was like that.

Robert Butler is online editor of Intelligent life