Credit Suisse Group's business underwriting blank-check Spacs boomed to start the year. That helped offset other huge problems — most notably a $5.5bn loss from the March collapse of Archegos Capital Management.

Now the market for Spacs — or special-purpose acquisition companies — has come off the boil, and new underwriting fees are threatening to dry up. Credit Suisse's Spac deals are being closely watched by investors and analysts, because revenue from them came to represent a large chunk of overall investment-banking revenue last year. That raised concerns that the fees and deal volume might not be sustainable.