On yesterday's commute between the office and Japanese evening class, my shifter cable for the rear derailleur snapped (so I rode back home single-speed style 😅).
Today I took it to a bike shop, and of course, the chain, the cassette and the derailleur itself were completely knackered (I actually trust this great Chinese guy at the shop, he never tried to sell me stuff if it's not needed, and always finds cheaper options, so I'm pretty sure he's not ripping me off).
But given the cost of the tube in London, even this slightly unplanned expense will easily pay for itself. The bike itself is 12 years old and has done about 25,000 km so far. 🚲