China's booming bike-sharing sector has hit a road-bump: thievery. Last week one start-up folded after 90 per cent of its bikes were stolen, and another began ramping up the deposits of riders who were careless with locks.

The rise of the smartphone-driven economy has led to a resurgence in bicycles on China’s streets — but unlike those of the Mao era, the new models come with a QR code on the frame. The bikes can only being unlocked after users scan the code using a proprietary app.

The Chinese craze for bike-sharing has spawned at least 10 start-ups with funding from international investors, plus dozens more copycats. The top two, Mobike and ofo, have built 11m bicycles — enough for every household in Beijing to have one — and raised over $2.1bn combined since launching a year ago.