Though the Direct Debit guarantee gives an automatic right to a no-questions asked instant refund.

Not even having a provably validly signed mandate protects merchants against a refund (merchants recourse is small claims court), so while it's a nuisance, and while some people do get de-frauded by not paying attention to their statements, the article overstates things: If he "lost" money it'll be because he chose not to demand a refund.