The perils of owning a Sonos system are few and far between, but if there's one big risk that comes with the multiroom audio brand, it's the fact that you can expand your array of speakers so easily.

It happened on Sunday as we walked across Clapham Common towards the Old Town. My 10-year-old daughter asked if we might go to a shop to get something called a “baw-tool of wah-taah”. I stopped dead ...