Finance workers are flocking to the encrypted messaging app Signal in droves. And some of the world’s largest financial services firms are getting in front of the trend by trialling new technology to monitor employee conversations on it.

Tens of thousands of workers at two global banks and one Asian lender will spend the next 12 weeks testing an app that enables compliance teams to track staff chats on Signal. The tech also includes the ability to track WhatsApp, already popular among City workers, and its rival Telegram.