Deutsche Bank's corporate spying probe is not the only mystery in German banking. Not so long ago, Berlin depicted the financial crisis as an Anglo-Saxon problem. Even as Berlin took a 25 per cent stake in Commerzbank and rescued Hypo Real Estate, finance minister Peer Steinbrück railed at state aid provided to banks elsewhere. Then he dismissed other countries' stress tests as worthless. In some ways, Mr Steinbrück's insouciance was understandable. Unlike elsewhere, German credit continued to expand – at least until the start of this year.

Yet now lending surveys show almost half of German companies battle to raise funds from lenders, in spite of ultra-low interest rates.

A latecomer to the credit crunch, Berlin's challenge is to keep German banks lending. Indeed, their relative inactivity helps explain the urgency of Mr Steinbrück's – unheeded – calls for European countries to relax bank capital requirements. The bind Germany faces is clear. If its banks need more capital, they have two choices. They can either shrink their balance sheets – as Deutsche, Germany's largest bank, is doing – or they can raise more equity, which German banks have so far been loath to do. That is partly because of the stigma attached to rights issues and partly because it can dilute shareholders. The obvious alternative is for Berlin to force banks to raise more capital. Unfortunately, Mr Steinbrück's half-hearted bad bank plan neither compels banks to take part nor frees up capital for more lending. Unsurprisingly, no bank has joined.