The CEOs of both the Swiss bank and the Japanese investor are personally involved in a high-stakes dispute between the two.

Credit Suisse and Softbank locked horns for months including directly through CEOs Thomas Gottstein and Masayoshi Son, respectively, before the Zurich-based bank elected to take its erstwhile client to court, the «Financial Times» (behind paywall) reported on Monday.

The Swiss wealth manager seeks to recoup $440 million from Softbank, the souring of a relationship that included investment banking as well as reportedly the wealthy Son as a private client. The dispute involves Greensill, the defunct supply chain financier backed by Softbank which is at the center of a $10.1 billion fund blow-up at Credit Suisse.

He Said Vs He Said

The U.K. outlet reported that Credit Suisse's CEO Thomas Gottstein met with Son in September, along with the bank's top man in Asia, Helman Sitohang. Ulrich Koerner, a former UBS top executive who was parachuted in to run the troubled asset management arm where Greensill's funds sat, was also present.

Credit Suisse is arguing a so-called material discrepancy during the meeting between Son's comments on Katerra and an email from Lex Greensill from two years ago, the «FT» reported, citing court documents. Specifically, the Swiss bank suggests Son approved an emergency financing for Katerra.

Rare Court Dispute

Katerra is a now-defunct construction company and former Greensill client which is one of three of Credit Suisse's most troublesome obligors. The bank is just north of 70 percent into liquidating its supply chain funds.

The court escalation underscores how high the stakes are for Credit Suisse: it is exceedingly rare for wealth managers to pursue their clients through the courts. The bank is currently engaged in another high-profile dispute with a client in Saudi Arabia.