in-built

That would make entering a PIN even more of a rarity, as smartphones - with extra in-built security - already have no limit on contactless payments via a digital wallet.

Paying this way already has an unlimited payment limit, owing to the in-built extra security features such as thumbprints or face ID.

One reason is a collectively very strong, in-built sense of "fairness", argues Professor Gina Neff from Cambridge University.

It has in-built crisis and escalation pathways whereby users are signposted to helplines or can send for help directly if they show signs of self-harm or suicidal ideation.

As for the in-built competitive edge, she says success depends on whether they can "play as a team rather than against each other."