Source of wealth is a mandatory requirement of any UK regulated casino, once a certain threshold has been met. Many casinos have been fined huged sums by the UKGC by not having sufficient KYC checks in place. If you refuse to send in bank statements, then you won’t be able to play, it’s as simple as that.
Casumo take this to a whole new level, however, with an obscene level of rechecks and an incompetent set of handlers.
I do support anyone who says to avoid Leo though, as they have abysmal customer service. ?