It’s the best kind of water to top up a pond with, because it’s lower in algae-stimulating nitrogen than tap water. It’s also ideal for watering patio pots and borders. And by keeping at least some storm water in your garden you’re reducing the effects of flash floods which can cause major problems in big cities, particularly London.

Collecting rainwater is easy. Just install a rain diverter and water butt (100-250 litres), propped up on blocks so you can get the watering can underneath. Many local authorities offer cheap water butts, but you can save much larger amounts (650-1250 litres) in the rectangular tanks which are available commercially.