Sometimes it’s fruity, sometimes it’s syrupy. It’s usually very sweet. And it’s always full of … tapioca. How did Taiwan’s ‘boba tea’ become such a hit everywhere from Cardiff to Glasgow?

On a sunny Thursday afternoon, the Covent Garden branch of Gong cha is doing a roaring trade. Staff behind the counter are busy preparing drinks for a string of customers, all ordering from an electronic pad in the corner. One leaves with a purple concoction flavoured with the root vegetable taro; another sips on a milky tea laced with brown sugar “pearls”. A third grabs a bright drink tasting of passion fruit and adorned with floating coconut jelly.

It’s a scene being played out more and more as bubble tea shops like Gong cha pop up around the UK. Wisbech, Cambridgeshire, has just got its first (called Just Poppin); in Canterbury, Kent, there are six shops to choose from; and a new branch of American bubble tea brand CoCo recently had dozens of people queueing down Glasgow’s Bath Street.