Time was when every smart urban patio was equipped with one of those gas-burning heaters of the type found outside London cafés. In this age of sensitivity to global warming we've come to be wary of them […], but somehow those strange little chimineas seem to have warmed the hearts of the nation. I've always found them a bit odd looking – like something from The Hobbit – and you do need to position them where they can do their job without endangering life, limb and property.