OpenAI Offers GPT-5.5 Cyber to 9 UK Banks as Anthropic Blocks Mythos Access
Updated
Updated · BBC.com · Jun 1
OpenAI Offers GPT-5.5 Cyber to 9 UK Banks as Anthropic Blocks Mythos Access
5 articles · Updated · BBC.com · Jun 1
Nine major UK banks have been offered OpenAI's GPT-5.5 Cyber after Anthropic kept them out of Claude Mythos previews, giving lenders a new way to probe hidden software vulnerabilities.
The offer follows Bank of England Governor Andrew Bailey's warning last week that UK banks still could not access Mythos to test their own systems and apps.
The AI Security Institute said GPT-5.5 Cyber and Mythos showed a similar level of performance, with both tools able to uncover hard-to-find weaknesses in legacy code.
Lloyds, HSBC and Nationwide are among the banks newly gaining access, while NatWest and Santander already had it; OpenAI said the tool would be shared selectively, not released broadly.
The dispute highlights growing concern that cyber AI powerful enough to do weeks of code review in minutes could strengthen defenses for banks while also posing wider financial-stability risks.
With AI finding countless flaws, how can legacy banks possibly fix them all in time?
Who governs the gatekeepers of AI that can both protect and cripple global financial systems?
GPT-5.5 Cyber vs. Claude Mythos: How AI Access Gaps Threaten UK Financial Security and Digital Sovereignty
Overview
In June 2026, OpenAI strategically offered its advanced GPT-5.5 Cyber model to major UK banks and global financial institutions, addressing urgent cybersecurity needs as threats escalate. This move comes as UK banks struggle to access Anthropic’s rival Claude Mythos, which remains limited to select organizations through Project Glasswing. The UK AI Security Institute has recognized both models as major advances in cyber capabilities, highlighting their importance for national and financial security. OpenAI’s broader access fills a critical gap, enabling UK banks to strengthen their defenses with cutting-edge AI at a time of growing global demand and regulatory attention.